Comprehensive isolation and functional analysis of the genes whose expressions are specifically induced upon entry into the Go phase of cell cycle

当培养基中胎牛血清浓度从10%降至0.5%时，哺乳动物细胞停止生长，进入静止期或G_0期。认为G_0期细胞的培养液中存在一定的增殖抑制因子，以维持静止状态。然而，关于G_0期的基因及其基因产物的研究却很少。因此，如果进行表达被诱导的基因的大规模分离，则可以分离通过生长抑制功能维持静止期所需的基因。为了全面地分离这些基因，我们使用了如我们先前所述的改进的cDNA文库消减法p。使用这种方法，我们迄今为止已经能够分离出超过60个基因，其表达在生长停滞条件下被诱导，并被称为生长停滞诱导的转录本，TIGA基因。一些TIGA基因的转录也在细胞生长的接触抑制后被诱导。TIGA基因之一TIGA1编码具有单个跨膜基序的小蛋白。Ecopically表达的Tiga1有效地抑制细胞生长。这些TIGA基因的功能分析将有助于了解细胞周期G_0期诱导和维持的分子机制。

Mammalian cells stops growth and enter into the static phase or G_0 phase when the concentration of fetal calf serum in the culture medium was reduced from 10% to 0.5%. It was believed that a certain proliferation inhibitory factors exist in the medium harboring the cells in the G_0 phase to maintain the static condition. However, very few studies have been reported on the genes and their gene products that define the G_0 phase. Thus, if a large scale isolation of the genes whose expression was induced is performed, it would be possible to isolate the gene that is required to maintain the static phase by growth-inhibitory function. To isolate such genes comprehensively, we used an improved cDNA library subtraction p as we described previously. Using this method, we have so far been able to isolate more than 60 genes whose expression is induced in growth arrest condition and termed the transcript induced in growth arrest, TIGA, genes. Transcription of some of the TIGA genes are also induced upon contact inhibition of the cell growth. One of the TIGA genes, TIGA1, encodes a small protein with a single transmembrane motif. Ecopically expressed Tiga1 potently inhibited cell growth. Functional analyses of these TIGA genes might shed light to understanding the molecular mechanisms of induction and maintenance of G_0 state of the cell cycle.