CDC6 IS AN UNSTABLE PROTEIN WHOSE DE-NOVO SYNTHESIS IN G(1) IS IMPORTANT FOR THE ONSET OF S-PHASE AND FOR PREVENTING A REDUCTIONAL ANAPHASE IN THE BUDDING YEAST SACCHAROMYCES-CEREVISIAE
CDC6 IS AN UNSTABLE PROTEIN WHOSE DE-NOVO SYNTHESIS IN G(1) IS IMPORTANT FOR THE ONSET OF S-PHASE AND FOR PREVENTING A REDUCTIONAL ANAPHASE IN THE BUDDING YEAST SACCHAROMYCES-CEREVISIAE
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DOI：
10.1002/j.1460-2075.1995.tb00048.x
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发表时间：
1995-08-01
期刊：
影响因子：
11.4
通讯作者：
NASMYTH, K
中科院分区：
文献类型：
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作者：
PIATTI, S;LENGAUER, C;NASMYTH, K
S期的进入依赖于细胞周期蛋白依赖性激酶，其在G（1）晚期的激活部分是由于不稳定的细胞周期蛋白亚基的合成。我们在这里确定了第二种类型的不稳定蛋白Cdc6，其在G（1）期间的合成对于DNA复制的起始是重要的。CDC6基因通常在有丝分裂结束时转录，但在G（1）期延长的细胞中，在G（1）晚期有第二次转录爆发。前者是由于Swi5，而后者是由于MBF或SBF转录因子。在G（1）晚期不能合成Cdc6的小G（1）细胞非常缓慢地通过8期。既不在有丝分裂末期也不在G（1）晚期转录CDC6的细胞不能复制DNA，但尽管如此，仍进行有丝分裂并产生具有部分DNA含量的子细胞。这种“还原”后期几乎以野生型动力学发生，并依赖于G（2）细胞周期蛋白的活性。因此，由于cdc6缺陷而不能复制染色体的细胞不能阻止有丝分裂的发生，这与其他具有复制缺陷的突变体不同。我们表明，通过荧光原位杂交，染色体保持不重复，由于缺乏Cdc6合成分离完整的纺锤体两极在“还原”后期。
S phase entry depends on cyclin-dependent kinases whose activation during late G(1) is due partly to the synthesis of unstable cyclin subunits. We identify here a second type of unstable protein, Cdc6, whose synthesis during G(1) is important for initiation of DNA replication. The CDC6 gene is normally transcribed at the end of mitosis, but in cells with a prolonged G(1) phase there is a second burst of transcription in late G(1). The former is due to Swi5, while the latter is due to MBF or SBF transcription factors. Small G(1) cells that cannot synthesize Cdc6 in late G(1) progress through 8 phase very slowly. Cells that transcribe CDC6 neither at the end of mitosis nor in late G(1) fail to replicate DNA but, despite this, undergo mitosis and produce daughter cells with fractional DNA contents. This 'reductional' anaphase occurs with almost wild-type kinetics and depends on the activity of G(2) cyclins. Thus, cells that fail to duplicate chromosomes due to a cdc6 defect cannot prevent the onset of mitosis, unlike other mutants with replication defects. We show, by fluorescence in situ hybridization, that chromosomes which remain unduplicated due to a lack of Cdc6 synthesis are segregated intact to spindle poles during the 'reductional' anaphase.