Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America.
PLoS One. 2012;7(11):e49626. doi: 10.1371/journal.pone.0049626. Epub 2012 Nov 26.
The protein Snm1B plays a key role in interstrand crosslink (ICL) repair. In a yeast two-hybrid screen we identified the protein PSF2 to bind Snm1B. PSF2 is a member of the GINS complex involved in replication initiation and elongation, and is known to play a role in ICL repair. Snm1B was shown to bind PSF2 in human cells through two regions, strongly to a 144 amino acid N-terminal region and weakly to a second smaller 37 amino acid C-terminal region. Ectopic expression of PSF2 increased the amount of Mus81, a protein component of the endonucleolytic complex involved in ICL repair, co-immunoprecipitating with Snm1B. Moreover, deleting the N-terminal, but not C-terminal region of Snm1B reduced the amount of co-immunoprecipitated Mus81. Conversely, the telomere-binding protein TRF2 competed with PSF2 for binding to the C-terminus of Snm1B, and deletion of this region, but not the N-terminal region, reduced Snm1B chromatin association. We speculate that the N-terminal region of Snm1B forms a complex containing PSF2 and Mus81, while the C-terminal region is important for PSF2-mediated chromatin association.
Snm1B 蛋白在链间交联（ICL）修复中发挥关键作用。在酵母双杂交筛选中，我们鉴定出与 Snm1B 结合的 PSF2 蛋白。PSF2 是参与复制起始和延伸的 GINS 复合物的成员，已知其在 ICL 修复中发挥作用。Snm1B 在人类细胞中通过两个区域与 PSF2 结合，与 144 个氨基酸的 N 端区域强烈结合，与第二个较小的 37 个氨基酸的 C 端区域弱结合。PSF2 的异位表达增加了 Mus81 的量，Mus81 是参与 ICL 修复的内切核酸酶复合物的蛋白质成分，与 Snm1B 共免疫沉淀。此外，删除 Snm1B 的 N 端，但不删除 C 端区域，减少了共免疫沉淀的 Mus81 的量。相反，端粒结合蛋白 TRF2 与 PSF2 竞争与 Snm1B 的 C 端结合，并且该区域的缺失，而不是 N 端区域的缺失，减少了 Snm1B 染色质的关联。我们推测 Snm1B 的 N 端区域形成包含 PSF2 和 Mus81 的复合物，而 C 端区域对于 PSF2 介导的染色质关联很重要。
