通过Mek1-Ndt80负反馈环协调酵母中的双链断裂修复和减数分裂进程

Coordination of Double Strand Break Repair and Meiotic Progression in Yeast by a Mek1-Ndt80 Negative Feedback Loop.

作者信息

Prugar Evelyn, Burnett Cameron, Chen Xiangyu, Hollingsworth Nancy M

机构信息

Department of Biochemistry and Cell Biology, Stony Brook University, New York 11794-5215.

Department of Biochemistry and Cell Biology, Stony Brook University, New York 11794-5215

出版信息

Genetics. 2017 May;206(1):497-512. doi: 10.1534/genetics.117.199703. Epub 2017 Mar 1.

Abstract

During meiosis, homologous chromosomes are physically connected by crossovers and sister chromatid cohesion. Interhomolog crossovers are generated by the highly regulated repair of programmed double strand breaks (DSBs). The meiosis-specific kinase Mek1 is critical for this regulation. Mek1 downregulates the mitotic recombinase Rad51, indirectly promoting interhomolog strand invasion by the meiosis-specific recombinase Dmc1. Mek1 also promotes the formation of crossovers that are distributed throughout the genome by interference and is the effector kinase for a meiosis-specific checkpoint that delays entry into Meiosis I until DSBs have been repaired. The target of this checkpoint is a meiosis-specific transcription factor, Ndt80, which is necessary to express the polo-like kinase and the cyclin thereby allowing completion of recombination and meiotic progression. This work shows that Mek1 and Ndt80 negatively feedback on each other such that when DSB levels are high, Ndt80 is inactive due to high levels of Mek1 activity. As DSBs are repaired, chromosomes synapse and Mek1 activity is reduced below a threshold that allows activation of Ndt80. Ndt80 transcription of results in degradation of Red1, a meiosis-specific protein required for Mek1 activation, thereby abolishing Mek1 activity completely. Elimination of Mek1 kinase activity allows Rad51-mediated repair of any remaining DSBs. In this way, cells do not enter Meiosis I until recombination is complete and all DSBs are repaired.

摘要

在减数分裂过程中,同源染色体通过交叉和姐妹染色单体黏连在物理上相连。同源染色体间的交叉是由程序性双链断裂(DSB)的高度调控修复产生的。减数分裂特异性激酶Mek1对这种调控至关重要。Mek1下调有丝分裂重组酶Rad51,间接促进减数分裂特异性重组酶Dmc1介导的同源染色体间链入侵。Mek1还通过干扰促进分布于整个基因组的交叉的形成,并且是减数分裂特异性检查点的效应激酶,该检查点会延迟进入减数分裂I,直到DSB得到修复。这个检查点的靶标是减数分裂特异性转录因子Ndt80,它对于表达polo样激酶和细胞周期蛋白是必需的,从而允许重组完成和减数分裂进程。这项工作表明,Mek1和Ndt80相互负反馈,使得当DSB水平较高时,由于Mek1活性较高,Ndt80处于无活性状态。随着DSB的修复,染色体发生联会,Mek1活性降低到允许Ndt80激活的阈值以下。Ndt80对的转录导致Red1降解,Red1是Mek1激活所需的减数分裂特异性蛋白,从而完全消除Mek1活性。Mek1激酶活性的消除允许Rad51介导修复任何剩余的DSB。通过这种方式,细胞直到重组完成且所有DSB都得到修复才进入减数分裂I。

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