Kong L-J, Chang J T, Bild A H, Nevins J R
Department of Molecular Genetics and Microbiology, Institute for Genome Sciences and Policy, Duke University Medical Center, Durham, NC 27710, USA.
Oncogene. 2007 Jan 18;26(3):321-7. doi: 10.1038/sj.onc.1209817. Epub 2006 Aug 14.
Functions encoded by single genes in lower organisms are often represented by multiple related genes in the mammalian genome. An example is the retinoblastoma and E2F families of proteins that regulate transcription during the cell cycle. Analysis of gene function using germline mutations is often confounded by overlapping function resulting in compensation. Indeed, in cells deleted of the E2F1 or E2F3 genes, there is an increase in the expression of the other family member. To avoid complications of compensatory effects, we have used small-interfering RNAs that target individual E2F proteins to generate a temporary loss of E2F function. We find that both E2F1 and E2F3 are required for cells to enter the S phase from a quiescent state, whereas only E2F3 is necessary for the S phase in growing cells. We also find that the acute loss of E2F3 activity affects the expression of genes encoding DNA replication and mitotic activities, whereas loss of E2F1 affects a limited number of genes that are distinct from those regulated by E2F3. We conclude that the long-term loss of E2F activity does lead to compensation by other family members and that the analysis of acute loss of function reveals specific and distinct roles for these proteins.
低等生物中由单个基因编码的功能，在哺乳动物基因组中通常由多个相关基因来体现。一个例子是在细胞周期中调节转录的视网膜母细胞瘤蛋白家族和E2F蛋白家族。利用种系突变分析基因功能，常常因功能重叠导致的补偿作用而变得复杂。实际上，在缺失E2F1或E2F3基因的细胞中，另一个家族成员的表达会增加。为避免补偿效应带来的复杂性，我们使用了靶向单个E2F蛋白的小干扰RNA，以暂时丧失E2F功能。我们发现，E2F1和E2F3都是细胞从静止状态进入S期所必需的，而在生长中的细胞中，只有E2F3是S期所必需的。我们还发现，E2F3活性的急性丧失会影响编码DNA复制和有丝分裂活动的基因的表达，而E2F1的丧失则影响有限数量的、与E2F3调控的基因不同的基因。我们得出结论，E2F活性的长期丧失确实会导致其他家族成员的补偿，并且对功能急性丧失的分析揭示了这些蛋白的特定和不同作用。
