Affiliation:
1. Department
of Biological Chemistry, University of California-Irvine, Irvine,
California 92697-1700
Abstract
ABSTRACT
We
constructed yeast strains in which rRNA gene repeats are integrated at
ectopic sites in the presence or absence of the native nucleolus. At
all three ectopic sites analyzed, near centromere
CEN5
, near
the telomere of chromosome VI-R, and in middle of chromosome V-R
(mid-V-R), a functional nucleolus was formed, and no difference in the
expression of rRNA genes was observed. When two ribosomal DNA (rDNA)
arrays are present, one native and the other ectopic, there is
codominance in polymerase I (Pol I) transcription. We also examined the
expression of a single rDNA repeat integrated into ectopic loci in
strains with or without the native
RDN1
locus. In a strain
with reduced rRNA gene copies at
RDN1
(∼40 copies),
the expression of a single rRNA gene copy near the telomere was
significantly reduced relative to the other ectopic sites, suggesting a
less-efficient recruitment of the Pol I machinery from the
RDN1
locus. In addition, we found a single rRNA gene at
mid-V-R was as active as that within the 40-copy
RDN1
.
Combined with the results of activity analysis of a single versus two
tandem copies at
CEN5
, we conclude that tandem repetition is
not required for efficient rRNA gene
transcription.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
25 articles.
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