Expansion and contraction of ribosomal DNA repeats in Saccharomyces cerevisiae:: requirement of replication fork blocking (Fob1) protein and the role of RNA polymerase I
Expansion and contraction of ribosomal DNA repeats in Saccharomyces cerevisiae:: requirement of replication fork blocking (Fob1) protein and the role of RNA polymerase I
复制标题
DOI：
10.1101/gad.12.24.3821
复制
发表时间：
1998-12-15
影响因子：
10.5
通讯作者：
Horiuchi, T
中科院分区：
文献类型：
--
作者：
Kobayashi, T;Heck, DJ;Horiuchi, T
酿酒酵母在串联重复中携带类似于150个拷贝的rDNA。结果发现，在rpa 135缺失突变体中RNA聚合酶I（Pol I）的一个必需亚基的缺失引发rDNA重复数逐渐减少到正常水平的一半左右。重新引入缺失的RPA 135基因诱导重复数逐渐增加回到正常水平。基因FOB 1被证明是必不可少的减少和增加的rDNA重复。FOB 1以前被证明是所需的复制叉阻断（RFB）活动在RFB位点的rDNA和重组热点（HOT 1）的活动。因此，DNA复制叉阻断似乎刺激重组，并在rDNA扩增/收缩和序列均质化中起重要作用，并且可能在一般重复序列的不稳定性中起重要作用。另一方面，RNA Pol I似乎控制重复序列的数量，可能是通过稳定rDNA的正常重复序列数量作为一个稳定的核仁结构。
Saccharomyces cerevisiae carries similar to 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. Gene FOB1 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 RFB site 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.