Sobol R W, Horton J K, Kühn R, Gu H, Singhal R K, Prasad R, Rajewsky K, Wilson S H
Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston 77555-1068, USA.
Nature. 1996 Jan 11;379(6561):183-6. doi: 10.1038/379183a0.
Synthesis of DNA by DNA polymerase-beta is distributive on single-stranded DNA templates, but short DNA gaps with a 5' PO4 in the gap are filled processively to completion. In vitro studies have suggested a role of beta-polymerase in different types of DNA repair. However, the significance of these studies to the in vivo role of beta-polymerase has remained unclear. Because genetic studies are essential for determining the physiological role of a gene, we established embryonic fibroblast cell lines homozygous for a deletion mutation in the gene encoding DNA polymerase-beta. Extracts from these cell lines were found to be defective in uracil-initiated base-excision repair. The beta-polymerase-deleted cells are normal in viability and growth characteristics, although they exhibit increased sensitivity to monofunctional DNA-alkylating agents, but not to other DNA-damaging agents. Both the deficiency in base-excision repair and hypersensitivity to DNA-alkylating agents are rescued following stable transfection with a wild-type beta-polymerase minitransgene. These studies demonstrate that beta-polymerase functions specifically in base-excision repair in vivo.
DNA聚合酶β在单链DNA模板上进行DNA合成时是分布性的，但间隙中带有5'磷酸基团的短DNA间隙可被持续性地填补直至完成。体外研究表明β聚合酶在不同类型的DNA修复中发挥作用。然而，这些研究对β聚合酶体内作用的意义仍不明确。由于遗传学研究对于确定一个基因的生理作用至关重要，我们建立了编码DNA聚合酶β的基因发生缺失突变的纯合胚胎成纤维细胞系。发现这些细胞系的提取物在尿嘧啶引发的碱基切除修复中存在缺陷。缺失β聚合酶的细胞在活力和生长特性方面正常，尽管它们对单功能DNA烷化剂表现出更高的敏感性，但对其他DNA损伤剂不敏感。在用野生型β聚合酶微型转基因进行稳定转染后，碱基切除修复缺陷和对DNA烷化剂的超敏感性均得到挽救。这些研究表明，β聚合酶在体内特异性地参与碱基切除修复。
