Peña-Gómez María José, Rodríguez-Martín Yaiza, Del Rio Oliva Marta, Wijesekara Hanthi Yodhara, Berrada Sara, Freire Raimundo, Masson Jean Yves, Reyes José Carlos, Costanzo Vincenzo, Rosado Iván V
Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville 41092, Spain.
Departamento de Genética, Facultad de Biologia, Universidad de Sevilla, Seville 41012, Spain.
Sci Adv. 2025 Mar 28;11(13):eads3227. doi: 10.1126/sciadv.ads3227. Epub 2025 Mar 26.
Apurinic/apyrimidinic (AP) sites and single-strand breaks arising from base excision repair (BER) during the misincorporation of damaged nucleobases may hinder replication fork stability in homologous recombination-deficient (HRD) cells. At templated AP sites, cross-links between the DNA and 5-hydroxymethylcytosine binding, embryonic stem cell-specific (HMCES) regulate replication fork speed, avoiding cytotoxic double-strand breaks. While the role of HMCES at the template DNA strand is well studied, its effects on nascent DNA are not. We provide evidence that HMCES-DNA-protein cross-links (DPCs) are detrimental to the BER-mediated removal of 5-hydroxymethyl-2'-deoxycytidine (5hmdC)-derived 5-hydroxymethyl-2'-deoxyuridine from replication forks. HRD cells have heightened HMCES-DPCs, which increase further upon 5hmdC exposure, suggesting that HMCES binds both spontaneous and 5hmdC-induced AP sites. HMCES depletion substantially suppresses 5hmdC-mediated replication fork defects, chromosomal aberrations, and cell death in HRD cells. This reveals that HMCES-DPCs are a source of BER-initiated single-stranded DNA gaps, which indicates that endogenous DPCs contribute to genomic instability in HRD tumors.
在受损核碱基错掺入过程中，碱基切除修复（BER）产生的无嘌呤/无嘧啶（AP）位点和单链断裂可能会阻碍同源重组缺陷（HRD）细胞中的复制叉稳定性。在模板化的AP位点，DNA与5-羟甲基胞嘧啶结合、胚胎干细胞特异性（HMCES）之间的交联调节复制叉速度，避免细胞毒性双链断裂。虽然HMCES在模板DNA链上的作用已得到充分研究，但其对新生DNA的影响尚未明确。我们提供的证据表明，HMCES-DNA-蛋白质交联（DPCs）不利于BER介导的从复制叉中去除5-羟甲基-2'-脱氧胞苷（5hmdC）衍生的5-羟甲基-2'-脱氧尿苷。HRD细胞中HMCES-DPCs水平升高，在暴露于5hmdC后进一步增加，这表明HMCES既能结合自发产生的AP位点，也能结合5hmdC诱导的AP位点。HMCES的缺失显著抑制了5hmdC介导的HRD细胞中的复制叉缺陷、染色体畸变和细胞死亡。这表明HMCES-DPCs是BER引发的单链DNA缺口的一个来源，这意味着内源性DPCs会导致HRD肿瘤中的基因组不稳定。
