Toone W M, Johnson A L, Banks G R, Toyn J H, Stuart D, Wittenberg C, Johnston L H
Division of Yeast Genetics, National Institute for Medical Research, London, UK.
EMBO J. 1995 Dec 1;14(23):5824-32. doi: 10.1002/j.1460-2075.1995.tb00270.x.
Control of G1 cyclin expression in Saccharomyces cerevisiae is mediated primarily by the transcription factor SBF (Swi4/Swi6). In the absence of Swi4 and Swi6 cell viability is lost, but can be regained by ectopic expression of the G1 cyclin encoding genes, CLN1 or CLN2. Here we demonstrate that the RME1 (regulator of meiosis) gene can also bypass the normally essential requirement for SBF. RME1 encodes a zinc finger protein which is able to repress transcription of IME1 (inducer of meiosis) and thereby inhibit cells from entering meiosis. We have found that expression of RME1 from a high copy number plasmid can specifically induce CLN2 expression. Deletion of RME1 alone shows no discernible effect on vegetative growth, however, deletion of RME1 in a swi6 delta swi4ts strain results in a lowering of the non-permissive temperature for viability. This suggests that Rme1 plays a significant but ancillary role in SBF in inducing CLN2 expression. We show that Rme1 interacts directly with the CLN2 promoter and have mapped the region of the CLN2 promoter required for Rme1-dependent activation. Consistent with Rme1 having a cell cycle role in G1, we have found that RME1 mRNA is synthesized periodically in the cell cycle, with maximum accumulation occurring at the M/G1 boundary. Thus Rme1 may act both to promote mitosis, by activating CLN2 expression, and prevent meiosis, by repressing IME1 expression.
酿酒酵母中G1细胞周期蛋白表达的调控主要由转录因子SBF（Swi4/Swi6）介导。在缺乏Swi4和Swi6的情况下，细胞活力丧失，但通过异位表达G1细胞周期蛋白编码基因CLN1或CLN2可恢复活力。在此我们证明，RME1（减数分裂调节因子）基因也可绕过对SBF通常必需的需求。RME1编码一种锌指蛋白，它能够抑制IME1（减数分裂诱导因子）的转录，从而抑制细胞进入减数分裂。我们发现，从高拷贝数质粒表达RME1可特异性诱导CLN2表达。单独缺失RME1对营养生长没有明显影响，然而，在swi6δswi4ts菌株中缺失RME1会导致细胞存活的非允许温度降低。这表明Rme1在诱导CLN2表达的SBF中起重要但辅助的作用。我们表明Rme1直接与CLN2启动子相互作用，并已确定了Rme1依赖性激活所需的CLN2启动子区域。与Rme1在G1期具有细胞周期作用一致，我们发现RME1 mRNA在细胞周期中周期性合成，在M/G1边界处积累最多。因此，Rme1可能既通过激活CLN2表达促进有丝分裂，又通过抑制IME1表达防止减数分裂。
