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Human Molecular Genetics Pages 1947-1952  

The Treacher Collins syndrome (TCOF1) gene product, treacle, is targeted to the nucleolus by signals in its C-terminus
Introduction
Results
   Cellular localization of treacle
Discussion
Materials And Methods
   GFP-fusion constructs
   Immunofluorescence
Acknowledgements
Abbreviations
References

The Treacher Collins syndrome (TCOF1) gene product, treacle, is targeted to the nucleolus by signals in its C-terminus

The Treacher Collins syndrome (TCOF1) gene product, treacle, is targeted to the nucleolus by signals in its C-terminus

Sara T. Winokur and Rita Shiang1,*

Department of Biological Chemistry, University of California, Irvine, CA 92697, USA and 1Department of Human Genetics, School of Medicine, PO Box 980033, Virginia Commonwealth University, Richmond, VA 23298-0033, USA

Received June 23, 1998; Revised and Accepted August 5, 1998

The TCOF1 gene product, treacle, responsible for the craniofacial disorder Treacher Collins syndrome, has been predicted to be a member of a class of nucleolar phosphoproteins based on its primary amino acid sequence. Treacle is a low complexity protein with ten repeating units of acidic and basic residues, each of which contains a large number of putative casein kinase 2 and protein kinase C phosphorylation sites. In addition, the C-terminus of treacle contains multiple putative nuclear localization signals. The overall structure of treacle, as well as sequence similarity to several nucleolar phosphoproteins, predicts that treacle is a member of this class of proteins. Using green fluorescent protein fusion constructs with the full-length and deleted domains of the murine homolog of treacle, we demonstrate that the cellular localization of treacle is nucleolar. This localization is mediated by the last 41 residues of the C-terminus (residues 1262-1302). At least two functional nuclear localization signals have been identified in the protein, one between residues 1176 and 1270 and the second within the last 32 residues of the protein (1271-1302). The nucleolar localization signal is disrupted by two constructs that split the C-terminal region between residues 1270 and 1271. This study provides the first direct analysis of treacle and demonstrates that the protein involved in TCOF1 is a nucleolar protein.

INTRODUCTION

Treacher Collins syndrome (TCOF1) is an autosomal dominant disorder of craniofacial development. The clinical features include hypoplasia of the facial bones, in particular the mandible and zygomatic complex, coloboma of the lower eyelid with a lack of eyelashes medial to the defect, downward slanting of the palpebral fissures, cleft palate and conductive hearing loss due to malformations of the auditory ossicles (1). The structures affected in TCOF1 arise from the first and second branchial arches that form during the first 4 weeks of development and are affected in a symmetrical manner (2). TCOF1 occurs at a frequency of 1/50 000 live births and is a highly penetrant disorder with a wide range of expressivity (3,4).

The gene responsible for TCOF1 has been cloned and encodes a 1411 amino acid protein, treacle (5-7). Treacle is a low complexity protein that has a 213 residue N-terminus followed by 10 repeating units of acidic and basic residues and a C-terminus with multiple putative nuclear localization signals (NLSs). These putative NLSs conform to one of two types of signals. One is a short four residue consensus sequence that mediates synthetic peptide translocation to the nucleus (K-R/K-X-R/K) (8). The second is a consensus bipartite signal that contains two regions of basic residues separated by 10 amino acids (9). An additional potential NLS is located in the N-terminus of the protein. Each repeating unit in the gene is confined to a single exon (exons 7-16). Within the repeat units are putative casein kinase 2 (CK2) and protein kinase C (PKC) phosphorylation sites (7,10-12). The putative CK2 phosphorylation sites are found in the same region in every repeat unit with the exception of both mouse and human exon 11.

The mouse homolog of the TCOF1 gene has also been identified (12). There is 74.3% nucleotide identity, 61.5% protein identity and 71% similarity between the human and the mouse genes. The highest identity between the two proteins is in the extreme N-terminus, the putative NLSs at the C-terminus and the CK2 phosphorylation sites within the repeated motifs. The mouse protein is 109 amino acids smaller than its human counterpart. Three gaps, one in the N-terminal region, one in the repeat region and one in the C-terminal region, account for the majority of the size difference. Isolation of the mouse cDNA enabled the expression pattern during mouse development to be elucidated. Whole mount in situ hybridization experiments demonstrate involvement of the murine tcof1 gene in the craniofacial complex during embryonic development (12).

Sequence similarity has been identified between treacle and two related nucleolar phosphoproteins Nopp140 in rat and xNopp180 in Xenopus (7,12-14). The similarity is predominantly in the putative CK2 and PKC phosphorylation sites in the repeated domains. Nopp140 is also a low complexity protein with 10 alternating acidic and basic repeat units and several NLSs in its C-terminus. Nopp140 has been shown to be an NLS-binding protein that travels on tracks between the cytoplasm and the nucleolus (13,15). It is thought to shuttle proteins involved in ribosome assembly that are synthesized in the cytoplasm, translocated to the nucleus and targeted to the nucleolus (13). The human (p130) and yeast (srp40) homologs of Nopp140 have also been cloned (16,17). Analysis of srp40 mutants in yeast predicts that it has a dispensable role in preribosome assembly or transport (18). Interestingly, Nopp140 also functions as a transcriptional activator of the [alpha]1 acid glycoprotein (AGP) gene in conjunction with a gene specific enhancer protein (19).

Although treacle demonstrates sequence similarity to Nopp140, the functional homology to this class of nucleolar phosphoproteins had not been analyzed. By fusing the murine tcof1 gene to green fluorescent protein (GFP), we have determined that the cellular localization of treacle is nucleolar and that the 41 most C-terminal amino acids are necessary and sufficient to direct that localization. We have also shown there are at least two functional NLSs in the last 127 residues of the protein. Furthermore, we have shown that residues affected in the most C-terminal mutation identified to date are involved in the nucleolar localization signal (NoLS) and that the functional NLSs flank this region. This study provides the first direct analysis of the protein treacle and demonstrates that the protein involved in TCOF1 is a nucleolar protein.

RESULTS

Cellular localization of treacle

In order to determine the subcellular localization of treacle and the regions of the protein that mediate this localization, we have generated a series of full-length and deletion GFP-treacle fusion constructs. Figure 1A depicts the constructs generated for this study and summarizes the subcellular localization of each construct. The amino acid sequence of the treacle C-terminus (Fig. 1B) allows for a comparison of the murine and human sequences and demarcates the breakpoints in the C-terminal deletion constructs.


Figure 1. (A)Protein structure of treacle showing the acidic-basic repeats in gray and the conserved putative NLSs and NoLS C-terminal region in black. The lines below the protein show the GFP-fusion constructs with the entire coding region of the gene and various deletion constructs. To the right of the constructs summarizes the localization of the constructs in the cell. (B) Amino acid comparison of the last 161 residues of the C-terminal region between the mouse and human treacle proteins. This amino acid sequence comprises the C fusion construct. The 1, 3 and 4 above the sequence designate the region where each of the C[Delta]1, C[Delta]3 and C[Delta]4 fusion constructs begins, respectively. The C[Delta]2 construct includes amino acids 1176-1270 and is the region designated by the two black arrowheads. The 4 bp NLS consensus sites are underlined, the conserved bipartite NLSs are shown in bold, and the putative NoLS is boxed.

Cos-1 cells were chosen for transfection as they have distinct nucleoli which can be seen as dense circular structures in the nucleus following DAPI staining. Figure 2A shows a field of two cells in which the dark crater-like nucleoli are surrounded by the brighter DAPI fluorescence of nucleic acid in the nucleoplasm. In order to unambiguously identify these structures as nucleoli, antibodies to the abundant nucleolar protein nucleophosmin (B23) were hybridized to the Cos-1 cells. Rhodamine (TRITC)-conjugated secondary antibody reveals the localization of B23 within the nucleolus (Fig. 2B), which appears as bright red fluorescence over the same DAPI-negative regions seen in Figure 2A.


Figure 2. Treacle-GFP fusion constructs transfected into Cos-1 cells. (A) DAPI-stained Cos-1 cells reveal punctate staining of nucleoli, which appear as dark circular orbs. (B) The same two cells in which the nucleoli are identified by rhodamine-conjugated IgG following detection with anti-B23 antibodies. (C) A dividing cell demonstrates localization of the NRCo construct to the cytoplasm. This same pattern of localization was seen with the GFP pS65T-C1 vector alone. (D) Four nuclei stained with DAPI in blue and their nucleoli visualized with anti-B23 antibodies in red. (E) The same cells demonstrate localization of the NRCoC construct containing the full-length treacle protein to the nucleoli. (F) Localization of the C construct to the nucleolus captured with a double band filter allowing visualization of both DAPI and GFP fluorescence. (G) The C[Delta]2 construct localizes throughout the nucleoplasm with faint nucleolar localization. (H) The C[Delta]3 construct mediates effective localization to the nucleolus, revealed by bright GFP fluorescence over the nucleoli. (I) The C[Delta]4 construct shows diffuse nuclear localization and faint nucleolar localization.

The GFP fusion construct encoding the entire treacle protein (NRCoC) shows intense signals in the nucleoli (Fig. 2E). This figure also exemplifies the transfection rate of roughly 25% in these experiments. The GFP vector alone (pS65T-C1) shows cytoplasmic localization (data not shown). To determine the residues of treacle that direct its localization to the nucleolus, various deletion constructs of treacle were also made (Fig. 1). The treacle N-terminus (N), the N-terminus and the acidic/basic repeat regions (NR) and the N-terminus, the acidic/basic repeats and C-terminal residues up to the first residue encoded by the C construct (NRCo) demonstrate cytoplasmic localization of the encoded fusion proteins. Figure 2C shows the cytoplasmic localization of the NRCo construct in a dividing cell. The C construct containing the 161 most C-terminal residues shows nucleolar localization similar to the construct containing the entire protein (Fig. 2F).

Additional deletion constructs within the C-terminus were constructed to further characterize the localization signals in this region. Localization to the nucleolus was seen with constructs C[Delta]1 and C[Delta]3 which contain the 127 and 41 most C-terminal residues respectively (C[Delta]1, data not shown; C[Delta]3, Fig. 2H). Two constructs containing adjacent portions of the C-terminus (C[Delta]2, C[Delta]4) show a diffuse nucleoplasm and faint nucleolar localization (Fig. 2G and I, respectively). These constructs are able to translocate into the nucleus but appear to have a weakened NoLS. C[Delta]2 is comprised of residues 1176-1270. This region contains four short NLS consensus sites but is missing the bipartite NLS consensus sequence in the mouse (Fig. 1B). The most C-terminal construct (C[Delta]4), comprising of the last 32 amino acids of treacle, contains the residues that are mutated in the most C-terminal mutation identified to date in the human gene (corresponding to residue 1271 in the mouse) (Fig. 1B) (20). The C[Delta]4 peptide has one bipartite and many 4 bp NLS consensus sequences.

DISCUSSION

Based on sequence homologies, the gene responsible for TCOF1 was predicted to belong to a family of nucleolar phosphoproteins. The cellular localization of murine treacle to the nucleolus provides the first direct evidence that treacle is part of this family of genes. The nucleolus has been shown to be the site of rRNA synthesis and preribosomal assembly. Nucleolar phosphoproteins are thought to play important roles in preribosome assembly, transport of ribosomal proteins from the cytoplasm to the nucleolus and transport of preribosomal units from the nucleolus to the cytoplasm (reviewed in ref. 21).

Treacle is predicted to have multiple NLSs in the C-terminus. We have shown that there are at least two functional NLSs from residues 1176 to 1302 that are sufficient for nuclear localization (Fig. 1). One NLS is located in region 1176-1270. This region contains four short (4 residue) NLSs. The second functional NLS is located within residues 1271-1302. This region contains multiple 4 residue NLSs and one bipartite NLS signal.

The NoLS is also located in the last 41 amino acids of the protein since construct C[Delta]3 shows correct cellular localization. There is no known consensus NoLS but a variety of signals mediate functional interactions with specific proteins or nucleic acids that confer localization to the nucleolus. In nucleolin (C23), two regions that interact with RNA were identified to be important in nucleolar localization. One region contains an RNA recognition motif (RRM) and the other region is a glycine/arginine rich domain. The RRM region is also known to be the region where C23 binds to second nucleolar phosphoprotein, B23 (22,23). A small region identified in the HIV tat protein seems to be important in nucleolar localization (QRRRAP) (24). Mutations in the first two arginines in this sequence abolish the NoLS of this protein. This domain has been shown to be the region required for B23 binding of tat (25). Of the other NoLSs that have been characterized, the common motif seems only to be that of a basic domain, some arginine rich and others lysine rich (26,27). The terminal 41 amino acids of treacle is a highly basic region containing 14 lysines. These residues are conserved in the human protein (Fig. 1B). A putative NoLS had been predicted in the protein (residues 1262-1277, corresponding to residues 1370-1386 in the human sequence) (Fig. 1B) (7). This domain is split in the C[Delta]2 and C[Delta]4 constructs and only a portion of the domain can confer nucleolar localization but with much less efficiency than the intact domain. Thus, it seems that once these proteins are localized to the nucleus then binding to RNA or another nucleolar phosphoprotein may be sufficient for nucleolar localization.

The location of this functional domain of treacle in the C-terminus has implications for disease pathogenesis. The majority of identified mutations create premature stop codons in the protein (20). Mutations have been identified along the whole length of the gene. It has been shown previously that nonsense mutations in a number of different genes reduce the transcript level of the mutant allele by affecting transcript stability (28-34). Thus, the lack of or reduced amount of transcript from the mutant allele could reduce the normal amount of protein product by half and haploinsufficiency of treacle may be one mutational mechanism. An exception to this phenomenon occurs if the premature termination codon is located within the last third of the exon proceeding the exon containing the native termination codon. If the mutation is located in that region then the mRNA is not degraded (29,35,36). Interestingly, the most C-terminal mutation identified to date in the TCOF1 gene is at residue 1379 (20). A 5 bp insertion changes the reading frame of the protein and creates a premature termination codon 13 residues downstream. This termination codon is 19 amino acids from the native stop codon. This mutation also disrupts the NoLS signal of treacle at the precise residue that is missing in the C[Delta]2 construct. The C[Delta]2 construct has nuclear but inefficient nucleolar localization (Fig. 2G). Thus, multiple mechanisms may be acting in TCOF1. If the mRNA of the mutant allele is unstable then haploinsufficiency may be the mechanism underlying the disorder. In addition, if some mutant alleles are stable due to the location of the mutation in the gene and a truncated protein is translated but is missing a completely functional NoLS, then the mutant protein would not be efficiently directed to the nucleolus. Thus, these mutations may cause their effect by having insufficient amounts of the protein in the proper location. The effect of nonsense mutations on an mRNA species is complex and must be studied carefully before correlations to phenotypic expression can be made.

Sequence homology predicts treacle to be a member of a family of nucleolar phosphoproteins and we have shown that the murine treacle is indeed a nucleolar protein. The possible functions of this class of proteins include nucleologenesis, the transport of proteins or ribosomal subunits between the nucleolus and cytoplasm and stage-specific transcription activation (13,15-19). Though ribosome assembly may be one important function of treacle, this does not preclude it from having other cellular functions similar to Nopp140. If treacle's sole function is related to the production of ribosomes which in turn affects the rate of protein translation, then how the global effects of this defect are manifested solely in the development of the craniofacial region remains a mystery. A high rate of protein translation may well be required in rapidly growing embryonic tissues. In other tissues of the body specific proteins may be able compensate for the function that treacle performs in the craniofacial region.

MATERIALS AND METHODS

GFP-fusion constructs

In order to determine the subcellular localization of treacle, GFP- fusion constructs were made encoding various protein domains of the murine treacle homolog. All treacle partial cDNAs were cloned into the GFP C-terminal protein fusion vector pS65T-C1 (Clontech, Palo Alto, CA). Constructs were as follows: N (N-terminal residues 1-240), 277 bp [lambda]4 (13) PmlI/PvuII fragment, and NR (N-terminus plus repeat region residues 1-830), 2.5 kb [lambda]4 PmlI/HincII fragment, both into pS65T-C1 vector digested with Ecl136II; NRCo (residues 1-1111 deleted for C-terminus only), 3.3 kb [lambda]4 PmlI/NgoM1 fragment into pS65T-C1 Ecl136II/XmaI vector; NRCoC (entire treacle), 3.5 kb [lambda]4 Pml1/SfiI and 523 bp 3[prime] RACE (13) SfiI/Pst1 fragments into pS65T-C1 Pml1/Pst1; C (C-terminal residues 1142-1302), 694 bp 3[prime] RACE Pst1 fragment into pS65T-C1 Pst1. C[Delta]1 (C-terminal residues 1176-1302), C[Delta]2 (residues 1176-1270), C[Delta]3 (residues 1262-1302) and C[Delta]4 (residues 1271-1302) were all constructed following Ecl136II/EcoRI digestion of PCR products and ligation into similarly digested pS65T-C1 vector. PCR products were generated with the following primers: C[Delta]1: MCRE.F2 5[prime]-CCAGATCTCGAGCTCTAGAAGCTGGGGCCCCAAAG-3[prime] and MCRE.R1 5[prime]-GGGGATCCTCTAGAGAATTCTCCGGAATCACACGGCAGGCTCGGCTGA-3[prime]; C[Delta]2: MCRE.F2 and MCRE.R2 5[prime]-GGGGATCCTCTAGAGAATTCTCCGGACTTTTTCTCCTTGTCTTTTTTTTTCTTGAG-3[prime]; C[Delta]3: MCRE.F3 5[prime]-CCAGATCTCGAGCTCTCAAGAAAAAAAAAGACAAGGAGAAAAAGG-3[prime] and MCRE.R1; C[Delta]4: MCRE.F4 5[prime]-CCAGATCTCGAGCTCTCGAAAAGAAGAAAGGAAAAAAGTC-CCTG-3[prime] and MCRE.R1.

Immunofluorescence

Cos-1 cells were grown to 75% confluency at 37°C in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum (FBS). Ten micrograms of each GFP-treacle fusion construct was electroporated into 8 × 105 cells resuspended into 10 mM Tris-DMEM, pH 7.6, at 1000 µF, 48[Omega] and 150 V. Cells were then plated onto coverslips and incubated at 375C in DMEM/10% FBS for 48 h. Cells were then washed three times with 1× PBS, fixed with 3.7% formaldehyde in 1× PBS for 30 min at room temperature, washed again three times in 1× PBS, stained with DAPI and mounted with ProLong Antifade (Molecular Probes, Eugene, OR). In order to identify the nucleoli, cells were permeabilized with 0.5% NP-40 for 5 min in 1× PBS, washed three times in 1× PBS, blocked with 1:100 horse serum in 3% BSA/1× PBS for 30 min at room temperature and washed again three times with 1× PBS. Anti-B23 (Santa Cruz Biotechnology, Santa Cruz, CA) was diluted 1:1000 in 3% BSA/1× PBS and incubated for 1 h at room temperature. Following three washes in 1× PBS, rhodamine-labeled (TRITC) conjugated anti-goat IgG (Sigma, St Louis, MO) was diluted 1:250 and incubated for 1 h at room temperature. Following three washes of 1× PBS, cells were stained with DAPI and mounted with ProLong Antifade (Molecular Probes). Slides were viewed with a Zeiss axioskop epifluorescence microscope equipped with a Zeiss plan neofluor oil immersion objective (63×) and a 1.6× optivar. Images were captured using the Oncor Imaging System (Gaithersburg, MD).

ACKNOWLEDGEMENTS

We thank Dr Michael Dixon for the [lambda]4 and 3[prime] RACE tcof1 cDNA clones; Drs Leslie M. Thompson, Kyoko Yokomori, Robert K. Moyzis, Erik D. Foehr and Mary G. Prieve for helpful discussions and Ulla Bengtsson for technical assistance. This work was partially supported by NIH grant 1RO1AR42377.

ABBREVIATIONS

AGP, [alpha]1 acid glycoprotein; BSA, bovine serum albumin; B23, nucleophosmin; CK2, casein kinase 2; C23, nucleolin; DMEM, Dulbecco's modified Eagle's medium; FBS, fetal bovine serum; GFP, green fluorescent protein; NLS, nuclear localization signal; NoLS, nucleolar localization signal; PKC, protein kinase C; RRM, RNA recognition motif; TCOF1, Treacher Collins syndrome.

REFERENCES

1. Rogers, R.O. (1964) Berry-Treacher Collins syndrome. A review of 200 cases. Br. J. Plast. Surg., 17, 109-137.

2. Moore, K.L. and Persaud, T.V.N. (1993) In The Developing Human. Clinically Oriented Embryology. W.B. Saunders, Philadelphia, PA, pp. 186-225.

3. Waardenburg, P.J., Franceschetti, A. and Klein, D. (1961) In Genetics and Ophthalmology. Charles C. Thomas Publisher, Springfield, IL, pp. 372-379.

4. Rovin, S., Dachi, S.F., Borenstein, D.B. and Cotter W.B. (1964) Mandibulofacial dysostosis, a familial study of five generations. J. Pediatr., 65, 215-221.

5. Treacher Collins Syndrome Collaborative Group (1996) Positional cloning of a gene involved in the pathogenesis of Treacher Collins syndrome. Nature Genet., 12, 130-136.

6. Dixon, J., Edwards, S.J., Anderson, I., Brass, A., Scambler, P.J. and Dixon, M.J. (1997) Identification of the complete coding sequence and genomic organization of the Treacher Collins syndrome gene. Genome Res., 7, 223-234. MEDLINE Abstract

7. Wise, C.A., Chiang, L.C., Paznekas, W.A., Sharma, M., Musy, M.M., Ashley, J.A., Lovett, M. and Jabs, E.W. (1997) TCOF1 gene encodes a putative nucleolar phosphoprotein that exhibits mutations in Treacher Collins syndrome throughout its coding region. Proc. Natl Acad. Sci. USA, 94, 3110-3115. MEDLINE Abstract

8. Chelsky, D., Ralph, R. and Jonak, G. (1989) Sequence requirements for synthetic peptide-mediated translocation to the nucleus. Mol. Cell Biol., 9, 2487-2492. MEDLINE Abstract

9. Robbins, J., Dilworth, S.M., Laskey, R.A. and Dingwall, C. (1991) Two interdependent basic domains in nucleoplasmin nuclear targeting sequence: identification of a class of bipartite nuclear targeting sequence. Cell, 64, 615-623. MEDLINE Abstract

10. Woodgett, J.R., Gould, K.L. and Hunter, T. (1986) Substrate specificity of protein kinase C. Use of synthetic peptides corresponding to physiological sites as probes for substrate recognition requirements. Eur. J. Biochem., 161, 177-184. MEDLINE Abstract

11. Kuenzel, E.A., Mulligan, J.A., Sommercorn, J. and Kreb, E.G. (1987) Substrate specificity determinants for casein kinase II as deduced from studies with synthetic peptides. J. Biol. Chem., 262, 9136-9140. MEDLINE Abstract

12. Dixon, J., Hovanes, K., Shiang, R. and Dixon, M.J. (1997) Sequence analysis, identification of evolutionary conserved motifs and expression analysis of murine tcof1 provide further evidence for a potential function for the gene and its human homologue, TCOF1. Hum. Mol. Genet., 6, 727-737. MEDLINE Abstract

13. Meier, U.T. and Blobel, G. (1992) Nopp140 shuttles on tracks between nucleolus and cytoplasm. Cell, 70, 127-138. MEDLINE Abstract

14. Cairns, C. and McStay, B. (1995) Identification and cDNA cloning of a Xenopus nucleolar phosphoprotein xNopp180, that is the homolog of the rat nucleolar protein Nopp140. J. Cell Sci., 108, 3339-3347. MEDLINE Abstract

15. Meier, U.T. and Blobel, G. (1990) A nuclear localization signal binding protein in the nucleolus. J. Cell Biol., 111, 2235-2245. MEDLINE Abstract

16. Pai, C.-Y., Chen, H.-K., Sheu, H.-L. and Yeh, N.-H. (1995) Cell cycle-dependent alterations of a highly phosphorylated nucleolar protein p130 are associated with nucleogenesis. J. Cell Sci., 108, 1911-1920. MEDLINE Abstract

17. Meier, U.T. (1996) Comparison of the rat nucleolar protein Nopp140 with its yeast homolog SRP40. J. Biol. Chem., 271, 19376-19384. MEDLINE Abstract

18. Ikonomova, R., Sommer, T. and Kepes, F. (1997) The Srp40 protein plays a dose-sensitive role in preribosome assembly or transport and depends on its carboxy-terminal domain for proper localization to the yeast nucleoskeleton. DNA Cell Biol., 16, 1161-1173. MEDLINE Abstract

19. Miau, L.-H., Chang, C.-J., Tsai, W.-H. and Lee, S.-C. (1997) Identification and characterization of a nucleolar phosphoprotein Nopp140, as a transcription factor. Mol. Cell. Biol., 17, 230-239. MEDLINE Abstract

20. Edwards, S.J., Gladwin, A.J. and Dixon, M.J. (1997) The mutational spectrum in Treacher Collins syndrome reveals a predominance of mutations that create a premature-termination codon. Am. J. Hum. Genet., 60, 515-524. MEDLINE Abstract

21. Scheer, U. and Weisenberger, D. (1994) The nucleolus. Current Opinion Cell Biol., 6, 354-359. MEDLINE Abstract

22. Schmidt-Zachmann, M.S. and Nigg, E.A. (1993) Protein localization to the nucleolus: a search for targeting domains in nucleolin. J. Cell Sci., 105, 799-806. MEDLINE Abstract

23. Li, Y.-P., Busch, R.K., Valdez, B.C. and Busch, H. (1996) C23 interacts with B23, a putative nucleolar-localization-signal-binding protein. Eur. J. Biochem., 237, 153-158. MEDLINE Abstract

24. Dang, C.V. and Lee, W.M.F. (1989) Nuclear and nucleolar targeting sequences of c-erb-A, c-myb, N-myc, p53, HSP70, and HIV tat proteins. J. Biol. Chem., 264, 18019-18023. MEDLINE Abstract

25. Li, Y.P. (1997) Protein B23 is an important human factor for the nucleolar localization of the human immunodeficiency virus protein Tat. J. Virol., 71, 4098-4102. MEDLINE Abstract

26. Quaye, I.K., Toku, S. and Tanaka, T. (1996) Sequence requirement for nucleolar localization of rat ribosomal protein L31. Eur. J. Cell Biol., 69, 151-155. MEDLINE Abstract

27. Liu, J.-L., Lee, L.F., Ye, Y., Qian, Z. and Kung, H.-J. (1997) Nucleolar and nuclear localization properties of a herpesvirus bZIP oncoprotein, MEQ. J. Virol., 71, 3188-3196. MEDLINE Abstract

28. Fowler, A.V. and Zabin, I. (1968) Beta-galactosidase: immunological studies of nonsense, missense and deletion mutations. J. Mol. Biol., 33, 35-47. MEDLINE Abstract

29. Losson, R. and Lacroute, F. (1979) Interference of nonsense mutations with eukaryotic messenger RNA stability. Proc. Natl Acad. Sci. USA, 76, 5134-4137. MEDLINE Abstract

30. Humphries, R.K., Ley, T.J., Anagnou, N.P., Baur, A.W. and Nienhuis, A.W. (1984) [Bgr]5-39 thalassemia gene: A premature termination codon causes [beta]-mRNA deficiency without affecting cytoplasmic [beta]-mRNA stability. Blood, 64, 23-32. MEDLINE Abstract

31. Takeshita, K., Forget, G.B., Scarpa, A. and Benz, E.J. Jr (1984) Intranuclear defect in [beta]-globin mRNA accumulation due to a premature translation termination codon. Blood, 64, 13-22. MEDLINE Abstract

32. Baumann, B., Potash, M.J. and Kohler, G. (1985) Consequences of frameshift mutations at the immunoglobulin heavy chain locus of the mouse. EMBO J., 4, 351-359. MEDLINE Abstract

33. Daar, I.O. and Maquat, L.E. (1988) Premature translation termination mediates triosephosphate isomerase RNA degradation. Mol. Cell Biol., 8, 802-813. MEDLINE Abstract

34. Urlaub, G., Mitchell, P.J., Ciudad, C.J. and Chasin, L.A. (1989) Nonsense mutations in the dihydrofolate reductase gene affect RNA processing. Mol. Cell Biol., 9, 2868-2880. MEDLINE Abstract

35. Cheng, J., Fogel-Petrovic, M. and Maquat, M.E. (1990) Translation to near the distal end of the penultimate exon is required for normal levels of spliced triosephosphate isomerase mRNA. Mol. Cell Biol., 10, 5215-5225. MEDLINE Abstract

36. Belgrader, P. and Maquat, L.E. (1994) Nonsense but not missense mutations can decrease the abundance of nuclear mRNA for the mouse major urinary protein, while both types of mutations can facilitate exon skipping. Mol. Cell Biol., 14, 6326-6336. MEDLINE Abstract

*To whom correspondence should be addressed. Tel: +1 804 828 9632; Fax: +1 804 828 3760; Email: rshiang@hsc.vcu.edu

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[Abstract] [Full Text] [PDF]

Home page
 J. Med. Genet.Home page
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Linkage and linkage disequilibrium searched for between non-syndromic cleft palate and four candidate loci
J. Med. Genet., June 1, 2003; 40(6): 464 - 468.
[Full Text] [PDF]

Home page
 J. Orthod.Home page
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J. Orthod., December 1, 2002; 29(4): 293 - 298.
[Abstract] [Full Text] [PDF]

Home page
 J. Med. Genet.Home page
A Splendore, E W Jabs, and M R Passos-Bueno
Screening of TCOF1 in patients from different populations: confirmation of mutational hot spots and identification of a novel missense mutation that suggests an important functional domain in the protein treacle
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[Full Text] [PDF]

Home page
 Hum Mol GenetHome page
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[Abstract] [Full Text] [PDF]

Home page
 CROBMHome page
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Regulation of Mandibular Growth and Morphogenesis
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[Abstract] [Full Text] [PDF]

Home page
 Mol. Biol. CellHome page
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Characterization of the Nucleolar Gene Product, Treacle, in Treacher Collins Syndrome
Mol. Biol. Cell, September 1, 2000; 11(9): 3061 - 3071.
[Abstract] [Full Text]

Home page
 Hum Mol GenetHome page
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Increased levels of apoptosis in the prefusion neural folds underlie the craniofacial disorder, Treacher Collins syndrome
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