Human Molecular Genetics, Vol 7, 609-617, Copyright © 1998 by Oxford University Press
A Yu, AD Bailey and AM Weiner
Infection of human cells with adenovirus 12 (Ad12), but not Ad2 or 5,
induces four specific sites of metaphase chromosome fragility: the U1 small
nuclear RNA (snRNA) genes (the RNU1 locus), the U2 snRNA genes (RNU2), the
U1 snRNA pseudogenes (PSU1) and the 5S rRNA genes (RN5S). Significantly,
each of these sites corresponds to a multigene family encoding a small,
abundant structural RNA. We and others have shown previously that
Ad12-induced fragility of the RNU2 locus requires U2 snRNA promoter
elements, viral early functions and p53 function, but not viral replication
or integration, Rb function or chromosomal sequences flanking the RNU2
locus. Remarkably, we now find that very low doses of actinomycin D (5-50
ng/ml) can phenocopy Ad12 infection: metaphase fragility of the RNU1 and
RNU2 loci is induced specifically in the absence of virus, and induction
also requires U2 promoter elements and p53 function. Concurrently, it has
been found by others that treatment with cytosine arabinoside (araC), but
not aphidicolin, can also phenocopy Ad12 infection. We propose that Ad12
infection, actinomycin D and araC all induce a similar or identical global
damage arrest signal (perhaps a modification or altered conformation of
p53) that preferentially interferes with metaphase condensation of the RNU1
and RNU2 loci. The RNU1 and RNU2 loci could be especially sensitive to this
global signal either because specialized U snRNA transcription factors
interact uniquely with the signal, or because the high concentration of
short, active transcription units hinders chromatin condensation.
ARTICLES
Metaphase fragility of the human RNU1 and RNU2 loci is induced by actinomycin D through a p53-dependent pathway
Department of Molecular Biophysics, Yale University, 266 Whitney Avenue, PO Box 208114, New Haven, CT 06520-8114, USA.
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