Maloisel Laurent, Fabre Francis, Gangloff Serge
CEA, DSV, iRCM, SIGRR, LERA, Fontenay-aux-Roses F-92265, France.
Mol Cell Biol. 2008 Feb;28(4):1373-82. doi: 10.1128/MCB.01651-07. Epub 2007 Dec 17.
DNA polymerases play a central role during homologous recombination (HR), but the identity of the enzyme(s) implicated remains elusive. The pol3-ct allele of the gene encoding the catalytic subunit of DNA polymerase delta (Poldelta) has highlighted a role for this polymerase in meiotic HR. We now address the ubiquitous role of Poldelta during HR in somatic cells. We find that pol3-ct affects gene conversion tract length during mitotic recombination whether the event is initiated by single-strand gaps following UV irradiation or by site-specific double-strand breaks. We show that the pol3-ct effects on gene conversion are completely independent of mismatch repair, indicating that shorter gene conversion tracts in pol3-ct correspond to shorter extensions of primed DNA synthesis. Interestingly, we find that shorter repair tracts do not favor synthesis-dependent strand annealing at the expense of double-strand-break repair. Finally, we show that the DNA polymerases that have been previously suspected to mediate HR repair synthesis (Polepsilon and Poleta) do not affect gene conversion during induced HR, including in the pol3-ct background. Our results argue strongly for the preferential recruitment of Poldelta during HR.
DNA聚合酶在同源重组(HR)过程中发挥核心作用,但涉及的具体酶的身份仍不清楚。编码DNA聚合酶δ(Poldelta)催化亚基的基因的pol3-ct等位基因突出了该聚合酶在减数分裂HR中的作用。我们现在探讨Poldelta在体细胞HR中的普遍作用。我们发现,无论该事件是由紫外线照射后的单链缺口引发还是由位点特异性双链断裂引发,pol3-ct都会影响有丝分裂重组过程中的基因转换片段长度。我们表明,pol3-ct对基因转换的影响完全独立于错配修复,这表明pol3-ct中较短的基因转换片段对应于引发的DNA合成的较短延伸。有趣的是,我们发现较短的修复片段并不利于以双链断裂修复为代价的合成依赖性链退火。最后,我们表明,先前怀疑介导HR修复合成的DNA聚合酶(Polepsilon和Poleta)在诱导的HR过程中不影响基因转换,包括在pol3-ct背景下。我们的结果有力地支持了HR过程中Poldelta的优先募集。
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