Colomina N, Garí E, Gallego C, Herrero E, Aldea M
Departament de Ciències Mèdiques Bàsiques, Universitat de Lleida, Rovira Roure 44, 25198 Lleida, Catalunya, Spain.
EMBO J. 1999 Jan 15;18(2):320-9. doi: 10.1093/emboj/18.2.320.
Diploid yeast cells switch from mitosis to meiosis when starved of essential nutrients. While G1 cyclins play a key role in initiating the mitotic cell cycle, entry into meiosis depends on Ime1, a transcriptional activator regulated by both nutritional and cell-type signals. We show here that G1 cyclins downregulate IME1 transcription and prevent the accumulation of the Ime1 protein within the nucleus, which results in repression of early-meiotic gene expression. As G1-cyclin deficient cells do not require nutrient starvation to undergo meiosis, G1 cyclin would exert its role by transmitting essential nutritional signals to Ime1 function. The existence of a negative cross-talk mechanism between mitosis and meiosis may help explain why these two developmental options are incompatible in budding yeast.
当缺乏必需营养物质时，二倍体酵母细胞会从有丝分裂转变为减数分裂。虽然G1周期蛋白在启动有丝分裂细胞周期中起关键作用，但进入减数分裂则依赖于Ime1，Ime1是一种受营养和细胞类型信号调控的转录激活因子。我们在此表明，G1周期蛋白下调IME1转录并阻止Ime1蛋白在细胞核内积累，这导致减数分裂早期基因表达受到抑制。由于缺乏G1周期蛋白的细胞无需营养饥饿即可进行减数分裂，G1周期蛋白可能通过将必需的营养信号传递给Ime1功能来发挥其作用。有丝分裂和减数分裂之间存在负向相互作用机制，这可能有助于解释为什么这两种发育途径在芽殖酵母中是不相容的。
