HMCES,也称为5hmC结合胚胎干细胞特异性蛋白,是一种重要的DNA修复因子。HMCES具有多种生物学功能,包括保护DNA免受损伤、参与DNA损伤修复和调控基因表达。
HMCES能够与单链DNA中的脱嘌呤位点形成共价交联,防止DNA断裂和基因组不稳定性。在DNA复制过程中,HMCES能够有效地保护脱嘌呤位点免受自发切割或APE1核酸内切酶的切割,从而维持基因组稳定性[2]。此外,HMCES还能够与双链DNA结构相互作用,通过其SOS反应相关肽酶(SRAP)结构域与DNA结合,参与DNA损伤修复过程[6]。
HMCES在DNA损伤修复中具有重要作用。研究表明,HMCES缺陷小鼠在B细胞中表现出正常的造血功能,但其在类转换重组(CSR)过程中通过微同源介导的替代末端连接(Alt-EJ)途径修复DNA双链断裂的能力显著受损[7]。HMCES通过其SRAP结构域介导Alt-EJ,该功能需要DNA结合,但独立于其自肽酶和DNA交联活性。此外,HMCES还能够抑制体细胞超突变过程中免疫球蛋白基因的缺失,促进抗原特异性抗体的产生[3]。
HMCES还具有转录调控功能。研究发现,HMCES能够与R-SMAD蛋白结合,共同定位于活性组蛋白标记处,但HMCES的染色质定位独立于nodal/activin或BMP信号。HMCES通过竞争性结合染色质,限制R-SMAD蛋白的结合,从而抑制其调控作用,影响TGF-β家族信号的转录调控网络[5]。
此外,HMCES的表达水平与多种疾病的预后相关。例如,在脉络膜黑色素瘤中,HMCES的表达水平与患者的总生存期、无进展生存期和无转移生存期显著相关。HMCES的表达水平还与染色体3、8q、6q和6p的拷贝数变异相关[8]。
综上所述,HMCES是一种重要的DNA修复因子,参与保护DNA免受损伤、参与DNA损伤修复和调控基因表达。HMCES在多种生物学过程中发挥重要作用,包括DNA损伤修复、免疫球蛋白基因的稳定性和TGF-β家族信号的转录调控。HMCES的表达水平与多种疾病的预后相关,为疾病的治疗和预防提供了新的思路和策略[1,2,3,4,5,6,7,8]。
参考文献:
1. Huang, Min Emma, Qin, Yining, Shang, Yafang, Yeap, Leng-Siew, Meng, Fei-Long. 2024. C-to-G editing generates double-strand breaks causing deletion, transversion and translocation. In Nature cell biology, 26, 294-304. doi:10.1038/s41556-023-01342-2. https://pubmed.ncbi.nlm.nih.gov/38263276/
2. Donsbach, Maximilian, Dürauer, Sophie, Grünert, Florian, Semlow, Daniel R, Stingele, Julian. 2023. A non-proteolytic release mechanism for HMCES-DNA-protein crosslinks. In The EMBO journal, 42, e113360. doi:10.15252/embj.2022113360. https://pubmed.ncbi.nlm.nih.gov/37519246/
3. Wu, Lizhen, Shukla, Vipul, Yadavalli, Anurupa Devi, Rao, Anjana, Schatz, David G. 2022. HMCES protects immunoglobulin genes specifically from deletions during somatic hypermutation. In Genes & development, 36, 433-450. doi:10.1101/gad.349438.122. https://pubmed.ncbi.nlm.nih.gov/35450882/
4. Yaneva, Denitsa, Sparks, Justin L, Donsbach, Maximilian, Stingele, Julian, Walter, Johannes C. . The FANCJ helicase unfolds DNA-protein crosslinks to promote their repair. In Molecular cell, 83, 43-56.e10. doi:10.1016/j.molcel.2022.12.005. https://pubmed.ncbi.nlm.nih.gov/36608669/
5. Liang, Tao, Bai, Jianbo, Zhou, Wei, Tao, Qinghua, Xi, Qiaoran. . HMCES modulates the transcriptional regulation of nodal/activin and BMP signaling in mESCs. In Cell reports, 40, 111038. doi:10.1016/j.celrep.2022.111038. https://pubmed.ncbi.nlm.nih.gov/35830803/
6. Halabelian, Levon, Ravichandran, Mani, Li, Yanjun, Aravind, L, Arrowsmith, Cheryl H. 2019. Structural basis of HMCES interactions with abasic DNA and multivalent substrate recognition. In Nature structural & molecular biology, 26, 607-612. doi:10.1038/s41594-019-0246-6. https://pubmed.ncbi.nlm.nih.gov/31235913/
7. Shukla, Vipul, Halabelian, Levon, Balagere, Sanjana, Rao, Anjana, Aravind, L. 2019. HMCES Functions in the Alternative End-Joining Pathway of the DNA DSB Repair during Class Switch Recombination in B Cells. In Molecular cell, 77, 384-394.e4. doi:10.1016/j.molcel.2019.10.031. https://pubmed.ncbi.nlm.nih.gov/31806351/
8. Luo, Huan, Ma, Chao, Shao, Jinping, Cao, Jing. 2020. Prognostic Implications of Novel Ten-Gene Signature in Uveal Melanoma. In Frontiers in oncology, 10, 567512. doi:10.3389/fonc.2020.567512. https://pubmed.ncbi.nlm.nih.gov/33194647/