Author:
Kobayashi Takehiko,Heck Denis J.,Nomura Masayasu,Horiuchi Takashi
Abstract
Saccharomyces cerevisiae carries ∼150 copies of rDNA in tandem repeats. It was found that the absence of an essential subunit of RNA polymerase I (Pol I) in rpa135 deletion mutants triggers a gradual decrease in rDNA repeat number to about one-half the normal level. Reintroduction of the missing RPA135 gene induced a gradual increase in repeat number back to the normal level. GeneFOB1 was shown to be essential for both the decrease and increase of rDNA repeats. FOB1 was shown previously to be required for replication fork blocking (RFB) activity at RFBsite in rDNA and for recombination hot-spot (HOT1) activity. Thus, DNA replication fork blockage appears to stimulate recombination and play an essential role in rDNA expansion/contraction and sequence homogenization, and possibly, in the instability of repeated sequences in general. RNA Pol I, on the other hand, appears to control repeat numbers, perhaps by stabilizing rDNA with the normal repeat numbers as a stable nucleolar structure.
Publisher
Cold Spring Harbor Laboratory
Subject
Developmental Biology,Genetics
Cited by
354 articles.
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