Hentges Pierre, Waller Helen, Reis Clara C, Ferreira Miguel Godinho, Doherty Aidan J
Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, UK.
Instituto Gulbenkian de Ciência, Oeiras 2781-901, Portugal.
Cell Rep. 2014 Dec 24;9(6):2011-7. doi: 10.1016/j.celrep.2014.11.044. Epub 2014 Dec 18.
Eukaryotic cells use two principal mechanisms for repairing DNA double-strand breaks (DSBs): homologous recombination (HR) and nonhomologous end-joining (NHEJ). DSB repair pathway choice is strongly regulated during the cell cycle. Cyclin-dependent kinase 1 (Cdk1) activates HR by phosphorylation of key recombination factors. However, a mechanism for regulating the NHEJ pathway has not been established. Here, we report that Xlf1, a fission yeast XLF ortholog, is a key regulator of NHEJ activity in the cell cycle. We show that Cdk1 phosphorylates residues in the C terminus of Xlf1 over the course of the cell cycle. Mutation of these residues leads to the loss of Cdk1 phosphorylation, resulting in elevated levels of NHEJ repair in vivo. Together, these data establish that Xlf1 phosphorylation by Cdc2(Cdk1) provides a molecular mechanism for downregulation of NHEJ in fission yeast and indicates that XLF is a key regulator of end-joining processes in eukaryotic organisms.
真核细胞利用两种主要机制修复DNA双链断裂（DSB）：同源重组（HR）和非同源末端连接（NHEJ）。在细胞周期中，DSB修复途径的选择受到严格调控。细胞周期蛋白依赖性激酶1（Cdk1）通过磷酸化关键重组因子来激活HR。然而，尚未建立调控NHEJ途径的机制。在此，我们报道裂殖酵母XLF直系同源物Xlf1是细胞周期中NHEJ活性的关键调节因子。我们表明，在细胞周期过程中，Cdk1磷酸化Xlf1 C末端的残基。这些残基的突变导致Cdk1磷酸化丧失，从而导致体内NHEJ修复水平升高。总之，这些数据表明Cdc2（Cdk1）对Xlf1的磷酸化提供了裂殖酵母中NHEJ下调的分子机制，并表明XLF是真核生物中末端连接过程的关键调节因子。
