Ohya Tomoko, Arai Hirokazu, Kubota Yoshino, Shinagawa Hideo, Hishida Takashi
Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
Genetics. 2008 Sep;180(1):41-50. doi: 10.1534/genetics.107.086249. Epub 2008 Aug 30.
The ESC2 gene encodes a protein with two tandem C-terminal SUMO-like domains and is conserved from yeasts to humans. Previous studies have implicated Esc2 in gene silencing. Here, we explore the functional significance of SUMO-like domains and describe a novel role for Esc2 in promoting genome integrity during DNA replication. This study shows that esc2Delta cells are modestly sensitive to hydroxyurea (HU) and defective in sister chromatid cohesion and have a reduced life span, and these effects are enhanced by deletion of the RRM3 gene that is a Pif1-like DNA helicase. esc2Delta rrm3Delta cells also have a severe growth defect and accumulate DNA damage in late S/G2. In contrast, esc2Delta does not enhance the HU sensitivity or sister chromatid cohesion defect in mrc1Delta cells, but rather partially suppresses both phenotypes. We also show that deletion of both Esc2 SUMO-like domains destabilizes Esc2 protein and functionally inactivates Esc2, but this phenotype is suppressed by an Esc2 variant with an authentic SUMO domain. These results suggest that Esc2 is functionally equivalent to a stable SUMO fusion protein and plays important roles in facilitating DNA replication fork progression and sister chromatid cohesion that would otherwise impede the replication fork in rrm3Delta cells.
ESC2基因编码一种具有两个串联C末端类SUMO结构域的蛋白质，并且从酵母到人类都保守存在。先前的研究表明Esc2参与基因沉默。在这里，我们探讨类SUMO结构域的功能意义，并描述Esc2在DNA复制过程中促进基因组完整性的新作用。这项研究表明，esc2Δ细胞对羟基脲（HU）有适度敏感性，在姐妹染色单体黏连方面存在缺陷，并且寿命缩短，而这些效应通过缺失作为Pif1样DNA解旋酶的RRM3基因而增强。esc2Δrrm3Δ细胞也有严重的生长缺陷，并在S期后期/G2期积累DNA损伤。相比之下，esc2Δ不会增强mrc1Δ细胞对HU的敏感性或姐妹染色单体黏连缺陷，反而部分抑制这两种表型。我们还表明，删除Esc2的两个类SUMO结构域会使Esc2蛋白不稳定并使其功能失活，但这种表型可被具有真实SUMO结构域的Esc2变体抑制。这些结果表明，Esc2在功能上等同于一种稳定的SUMO融合蛋白，并且在促进DNA复制叉进展和姐妹染色单体黏连方面发挥重要作用，否则会在rrm3Δ细胞中阻碍复制叉。
