基因组完整性的维持依赖于多个DNA修复途径以及检查点调节。通过DNA损伤激活检查点激酶Chk1和Chk2触发细胞周期停滞和改善DNA修复,或在过度损伤的情况下凋亡。据报道,Chk1和Chk2以互补或冗余的方式起作用,取决于生理背景。在B淋巴细胞的次级免疫球蛋白(Ig)多样化过程中,DNA损伤是通过激活诱导的胞苷脱氨酶(AID)大量引入的,并通过几种易错的DNA修复途径以基因座特异性方式加工成突变。我们先前已经表明,Chk1通过促进无错同源重组和Ig基因转换来负调节Ig体细胞超突变。我们现在报告Chk2在这些过程的调节中显示出与Chk1相反的作用。B细胞中Chk2失活导致Ig超突变和Ig类别转换减少,并增加Ig基因转化活性。这与非同源末端连接中的缺陷和在干扰Chk2功能时增加的Chk1活化有关。有趣的是,在Ig多样化期间将大量DNA损伤生理引入基因组的背景下,因此,2个检查点激酶以相反的方式起作用,而不是冗余或合作。
Maintenance of genome integrity relies on multiple DNA repair pathways as well as on checkpoint regulation. Activation of the checkpoint kinases Chk1 and Chk2 by DNA damage triggers cell cycle arrest and improved DNA repair, or apoptosis in case of excessive damage. Chk1 and Chk2 have been reported to act in a complementary or redundant fashion, depending on the physiological context. During secondary immunoglobulin (Ig) diversification in B lymphocytes, DNA damage is abundantly introduced by activation-induced cytidine deaminase (AID) and processed to mutations in a locus-specific manner by several error-prone DNA repair pathways. We have previously shown that Chk1 negatively regulates Ig somatic hypermutation by promoting error-free homologous recombination and Ig gene conversion. We now report that Chk2 shows opposite effects to Chk1 in the regulation of these processes. Chk2 inactivation in B cells leads to decreased Ig hypermutation and Ig class switching, and increased Ig gene conversion activity. This is linked to defects in non-homologous end joining and increased Chk1 activation upon interference with Chk2 function. Intriguingly, in the context of physiological introduction of substantial DNA damage into the genome during Ig diversification, the 2 checkpoint kinases thus function in an opposing manner, rather than redundantly or cooperatively.