Characterization of two highly similar Rad51 homologs of Physcomitrella patens
Characterization of two highly similar Rad51 homologs of Physcomitrella patens
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DOI：
10.1006/jmbi.2001.5336
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发表时间：
2002-02-08
影响因子：
5.6
通讯作者：
Alonso, JC
中科院分区：
文献类型：
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作者：
Ayora, S;Piruat, JI;Alonso, JC
藓类植物小立碗藓（Physcomitrella patens）是一种具有高效同源重组的陆生植物，其编码两种Rad 51蛋白（PpaRad51.1和PpaRad51.2）。PpaRad51.1和PpaRad51.2蛋白质之间有94%的同一性，它们彼此相互作用。这两种蛋白质均以Mg 2+和pH依赖性方式结合ssDNA和dsDNA，化学计量分别类似托内每3（+/-1）nt或bp一个PpaRad51.1单体和每1（+/-0.5）nt或bp一个PpaRad51.2单体。在中性pH下，ssDNA和dsDNA结合需要1.6倍过量的两种蛋白质。PpaRad51.1和PpaRad51.2显示ssDNA依赖的ATP酶活性，并以核苷酸非依赖但Mg 2+依赖的方式有效地促进链退火。这两种蛋白质促进联合分子形成，DNA链侵入，并能够在Mg 2+和ATP存在下催化链交换。当两种蛋白质存在于同一反应中时，未观察到活性的进一步增加。没有PpaRad 51基因产物补充酿酒酵母rad 51 Delta突变体的DNA修复和重组表型。然而，PpaRad51.1赋予显性负性DNA修复表型，并且当在S.酿酒酵母wt细胞。这些结果表明，这两个PpaRad 51蛋白是真正的Rad 51蛋白，可能有助于，以不同的方式，同源重组，他们可能会取代ScRad 51在一个假设的酵母蛋白复合物灭活重组修复所需的不同功能。(C)2002年爱思唯尔科学有限公司
The moss Physcomitrella patens, which is a land plant with efficient homologous recombination, encodes two Rad51 proteins PpaRad51.1 and PpaRad51.2). The PpaRad51.1 and PpaRad51.2 proteins, which share 94% identity between them, interact with themselves and with each other. Both proteins bind ssDNA and dsDNA in a Mg2+ and pH-dependent manner, with a stoichiometry of similar toone PpaRad51.1 monomer per 3(+/-1) nt or bp and one PpaRad51.2 monomer per 1(+/-0.5) nt or bp, respectively. At neutral pH, a 1.6-fold excess of both proteins is required for ssDNA and dsDNA binding. PpaRad51.1 and PpaRad51.2 show ssDNA-dependent ATPase activity and efficiently promote strand annealing in a nucleotide-independent but in a Mg2+-depenclent manner. Both proteins promote joint-molecule formation, DNA strand invasion and are able to catalyse strand exchange in the presence of Mg2+ and ATP. No further increase in the activities is observed when both proteins are present in the same reaction. None of the PpaRad51 gene products complement the DNA repair and recombination phenotype of Saccharomyces cerevisiae rad51Delta mutants. However, PpaRad51.1 confers a dominant-negative DNA repair phenotype, and both PpaRad51 proteins reduce the levels of double-strand break-induced recombination when overexpressed in S. cerevisiae wt cells. These results suggest that both PpaRad51 proteins are bona fide Rad51 proteins that may contribute, in a different manner, to homologous recombination, and that they might replace ScRad51 in a hypothetical yeast protein complex inactivating different functions required for recombinational repair. (C) 2002 Elsevier Science Ltd.