Regulation of the mRNA levels of nimA, a gene required for the G2-M transition in Aspergillus nidulans.
Regulation of the mRNA levels of nimA, a gene required for the G2-M transition in Aspergillus nidulans.
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DOI：
10.1083/jcb.104.6.1495
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发表时间：
1987-06
期刊：
影响因子：
--
通讯作者：
Morris NR
中科院分区：
文献类型：
--
作者：
Osmani SA;May GS;Morris NR
温度敏感的细胞周期突变nimA 5导致构巢曲霉的细胞核在限制性温度下被阻断在G2晚期。在这些条件下，纺锤体极体分裂，但不分离，有丝分裂指数下降到零。如果nimA 5被阻断一个以上的倍增时间，然后从限制温度转换到允许温度，细胞核立即进入有丝分裂，有丝分裂纺锤体形成，染色体浓缩（奥克利，B. R.，和N. R. Morris，1983，J. Cell Biol.，96：1155-8）。我们通过DNA介导的nimA 5突变表型互补克隆了野生型nimA基因，并通过北方印迹分析表征了nimA mRNA表达。该转录本长3.6kb，受核周期的严格调控。在同步分裂的细胞中，nimA mRNA的水平随着细胞进入有丝分裂而升高，并且随着细胞进行有丝分裂而急剧下降。用羟基脲阻断在S期的细胞具有非常低水平的nimA mRNA。无论是通过抗有丝分裂剂苯菌灵还是通过细胞周期突变bimE 7阻断有丝分裂的细胞，都维持nimA转录物的升高水平。这些数据表明，不仅需要nimA进入有丝分裂，但因为转录本通常是周期性表达，并在细胞周期的严格控制下，他们建议，nimA可能在有丝分裂的启动中发挥调节作用。
The temperature-sensitive cell cycle mutation nimA5 causes nuclei of Aspergillus nidulans to be blocked in late G2 at restrictive temperature. Under these conditions the spindle pole body divides but does not separate and the mitotic index drops to zero. If nimA5 is blocked for more than one doubling time and then shifted from restrictive to permissive temperature, nuclei immediately enter mitosis, the mitotic spindle forms, and the chromosomes condense (Oakley, B. R., and N. R. Morris, 1983, J. Cell Biol., 96:1155-8). We have cloned the wild-type nimA gene by DNA-mediated complementation of the nimA5 mutant phenotype and have characterized nimA mRNA expression by Northern blot analysis. The transcript is 3.6 kb in length and is under tight nuclear cycle regulation. In synchronously dividing cells, the levels of nimA mRNA become elevated as cells enter mitosis and drop sharply as cells progress through mitosis. Cells blocked in S-phase with hydroxyurea have very low levels of nimA mRNA. Cells blocked in mitosis, either by the antimitotic agent benomyl or by the cell cycle mutation bimE7, maintain elevated levels of the nimA transcript. These data demonstrate not only that nimA is required for entry into mitosis, but because the transcript is normally expressed cyclically and is under tight cell cycle control, they suggest that nimA may play a regulatory role in the initiation of mitosis.