Bondar Tanya, Mirkin Ekaterina V, Ucker David S, Walden William E, Mirkin Sergei M, Raychaudhuri Pradip
Department of Biochemistry, University of Illinois, Chicago, Illinois 60612, USA.
J Biol Chem. 2003 Sep 26;278(39):37006-14. doi: 10.1074/jbc.M303003200. Epub 2003 Jul 10.
Schizosaccharomyces pombe Ddb1 is homologous to the mammalian DDB1 protein, which has been implicated in damaged-DNA recognition and global genomic repair. However, a recent study suggested that the S. pombe Ddb1 is involved in cell division and chromosomal segregation. Here, we provide evidence that the S. pombe Ddb1 is functionally linked to the replication checkpoint control gene cds1. We show that the S. pombe strain lacking ddb1 has slow growth due to delayed replication progression. Flow cytometric analysis shows an extensive heterogeneity in DNA content. Furthermore, the Deltaddb1 strain is hypersensitive to UV irradiation in S phase and is unable to tolerate a prolonged replication block imposed by hydroxyurea. Interestingly, the Deltaddb1 strain exhibits a high level of the Cds1 kinase activity during passage through S phase. Moreover, mutation of the cds1 gene relieves the defects observed in Deltaddb1 strain. The results suggest that many of the defects observed in Deltaddb1 cells are linked to an aberrant activation of Cds1, and that Ddb1 is functionally linked to Cds1.
粟酒裂殖酵母Ddb1与哺乳动物DDB1蛋白同源，后者与受损DNA识别及全基因组修复有关。然而，最近一项研究表明，粟酒裂殖酵母Ddb1参与细胞分裂和染色体分离。在此，我们提供证据表明，粟酒裂殖酵母Ddb1在功能上与复制检查点控制基因cds1相关。我们发现，缺乏ddb1的粟酒裂殖酵母菌株由于复制进程延迟而生长缓慢。流式细胞术分析显示DNA含量存在广泛的异质性。此外，Δddb1菌株在S期对紫外线照射高度敏感，并且无法耐受羟基脲施加的长时间复制阻滞。有趣的是，Δddb1菌株在通过S期时表现出高水平的Cds1激酶活性。此外，cds1基因突变可缓解在Δddb1菌株中观察到的缺陷。结果表明，在Δddb1细胞中观察到的许多缺陷与Cds1的异常激活有关，并且Ddb1在功能上与Cds1相关。
