The MER3 Helicase Involved in Meiotic Crossing Over Is Stimulated by Single-stranded DNA-binding Proteins and Unwinds DNA in the 3′ to 5′ Direction*
The MER3 Helicase Involved in Meiotic Crossing Over Is Stimulated by Single-stranded DNA-binding Proteins and Unwinds DNA in the 3′ to 5′ Direction*
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DOI：
10.1074/jbc.m104003200
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发表时间：
2001-08
期刊：
影响因子：
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通讯作者：
T. Nakagawa;H. Flores-Rozas;R. Kolodner
中科院分区：
文献类型：
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作者：
T. Nakagawa;H. Flores-Rozas;R. Kolodner
酿酒酵母减数分裂特异的MER3蛋白是进行杂交所必需的，这确保了同源染色体在第一次减数分裂时的忠实分离。MER3蛋白的预测序列包含DExH-box类型的DNA/RNA解旋酶的7个基序。纯化的MER3蛋白是一种DNA解旋酶，它可以取代50个核苷酸的片段，使其变成单链环状DNA。MER3具有ATPase活性，其活性受单链和双链DNA的刺激。在任何一种∼存在下，三磷酸腺苷水解酶的转化率为DNA500次/分钟。只有在酿酒酵母单链DNA结合蛋白RPA(复制蛋白A)存在的情况下，MER3才能有效地置换单链环状DNA中较长的631个核苷酸片段。RPA似乎抑制了MER3解旋酶单链产物的再退火。相对于DNA底物中的单链区域，MER3解旋酶可以在3‘到5’方向解开DNA。讨论了MER3解旋酶在减数分裂互换中的可能作用。
The meiosis-specific MER3 protein ofSaccharomyces cerevisiae is required for crossing over, which ensures faithful segregation of homologous chromosomes at the first meiotic division. The predicted sequence of the MER3 protein contains the seven motifs characteristic of the DExH-box type of DNA/RNA helicases. The purified MER3 protein is a DNA helicase, which can displace a 50-nucleotide fragment annealed to a single-stranded circular DNA. MER3 was found to have ATPase activity, which was stimulated either by single- or double-stranded DNA. The turnover rate,kcat , of ATP hydrolysis was ∼500/min in the presence of either DNA. MER3 was able to efficiently displace relatively long 631-nucleotide fragments from single-stranded circular DNA only in the presence of the S. cerevisiaesingle-stranded DNA-binding protein, RPA (replication protein A). It appears that RPA inhibits re-annealing of the single-stranded products of the MER3 helicase. The MER3 helicase was found to unwind DNA in the 3′ to 5′ direction relative to single-stranded regions in the DNA substrates. Possible roles for the MER3 helicase in meiotic crossing over are discussed.