Donaldson A D, Raghuraman M K, Friedman K L, Cross F R, Brewer B J, Fangman W L
Department of Genetics, University of Washington, Seattle 98195-7360, USA.
Mol Cell. 1998 Aug;2(2):173-82. doi: 10.1016/s1097-2765(00)80127-6.
Replication origins in chromosomes are activated at specific times during the S phase. We show that the B-type cyclins are required for proper execution of this temporal program. clb5 cells activate early origins but not late origins, explaining the previously described long clb5 S phase. Origin firing appears normal in cIb6 mutants. In clb5 clb6 double mutant cells, the late origin firing defect is suppressed, accounting for the normal duration of the phase despite its delayed onset. Therefore, Clb5p promotes the timely activation of early and late origins, but Clb6p can activate only early origins. In clb5 clb6 mutants, the other B-type cyclins (Clb1-4p) promote an S phase during which both early and late replication origins fire.
染色体中的复制起点在S期的特定时间被激活。我们发现B型细胞周期蛋白是正确执行这一时期程序所必需的。clb5细胞激活早期起点但不激活晚期起点，这解释了之前所描述的clb5细胞较长的S期。在cIb6突变体中，起点激发似乎正常。在clb5 clb6双突变体细胞中，晚期起点激发缺陷被抑制，这解释了尽管S期开始延迟但其持续时间正常的原因。因此，Clb5p促进早期和晚期起点的及时激活，但Clb6p只能激活早期起点。在clb5 clb6突变体中，其他B型细胞周期蛋白（Clb1 - 4p）促进一个S期，在此期间早期和晚期复制起点都会激发。
