Du W, Dyson N
MGH Cancer Center, Building 149, 13th Street, Charlestown, MA 02129, USA.
EMBO J. 1999 Feb 15;18(4):916-25. doi: 10.1093/emboj/18.4.916.
The first appearance of G1 during Drosophila embryogenesis, at cell cycle 17, is accompanied by the down-regulation of E2F-dependent transcription. Mutant alleles of rbf were generated and analyzed to determine the role of RBF in this process. Embryos lacking both maternal and zygotic RBF products show constitutive expression of PCNA and RNR2, two E2F-regulated genes, indicating that RBF is required for their transcriptional repression. Despite the ubiquitous expression of E2F target genes, most epidermal cells enter G1 normally. Rather than pausing in G1 until the appropriate time for cell cycle progression, many of these cells enter an ectopic S-phase. These results indicate that the repression of E2F target genes by RBF is necessary for the maintenance but not the initiation of a G1 phase. The phenotype of RBF-deficient embryos suggests that rbf has a function that is complementary to the roles of dacapo and fizzy-related in the introduction of G1 during Drosophila embryogenesis.
在果蝇胚胎发育过程中，G1期首次出现在细胞周期17，同时伴随着E2F依赖转录的下调。生成并分析了rbf的突变等位基因，以确定RBF在此过程中的作用。缺乏母源和合子RBF产物的胚胎显示出PCNA和RNR2这两个E2F调控基因的组成型表达，表明RBF是它们转录抑制所必需的。尽管E2F靶基因普遍表达，但大多数表皮细胞正常进入G1期。这些细胞中的许多不是在G1期暂停直到细胞周期进展的合适时间，而是进入异位S期。这些结果表明，RBF对E2F靶基因的抑制对于维持G1期是必要的，但不是启动G1期所必需的。RBF缺陷胚胎的表型表明，rbf具有与dacapo和fizzy-related在果蝇胚胎发育过程中引入G1期的作用互补的功能。
