Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center Science Park, and the Graduate School of Biomedical Sciences at Houston, Smithville Texas, P.O. Box 389, Smithville, TX 78957, USA.
Nucleic Acids Res. 2012 May;40(10):4473-82. doi: 10.1093/nar/gks054. Epub 2012 Feb 7.
Unique among translesion synthesis (TLS) DNA polymerases, pol ζ is essential during embryogenesis. To determine whether pol ζ is necessary for proliferation of normal cells, primary mouse fibroblasts were established in which Rev3L could be conditionally inactivated by Cre recombinase. Cells were grown in 2% O(2) to prevent oxidative stress-induced senescence. Cells rapidly became senescent or apoptotic and ceased growth within 3-4 population doublings. Within one population doubling following Rev3L deletion, DNA double-strand breaks and chromatid aberrations were found in 30-50% of cells. These breaks were replication dependent, and found in G1 and G2 phase cells. Double-strand breaks were reduced when cells were treated with the reactive oxygen species scavenger N-acetyl-cysteine, but this did not rescue the cell proliferation defect, indicating that several classes of endogenously formed DNA lesions require Rev3L for tolerance or repair. T-antigen immortalization of cells allowed cell growth. In summary, even in the absence of external challenges to DNA, pol ζ is essential for preventing replication-dependent DNA breaks in every division of normal mammalian cells. Loss of pol ζ in slowly proliferating mouse cells in vivo may allow accumulation of chromosomal aberrations that could lead to tumorigenesis. Pol ζ is unique amongst TLS polymerases for its essential role in cell proliferation.
在跨损伤合成（TLS）DNA 聚合酶中，聚合酶 ζ是胚胎发生过程中所必需的。为了确定聚合酶 ζ 是否对正常细胞的增殖是必要的，通过 Cre 重组酶使 Rev3L 可条件性失活，建立了原代小鼠成纤维细胞。细胞在 2%的 O(2)中生长，以防止氧化应激诱导的衰老。细胞迅速衰老或凋亡，并在 3-4 次细胞倍增后停止生长。在 Rev3L 缺失后的一个细胞倍增中，发现 30-50%的细胞中存在 DNA 双链断裂和染色单体畸变。这些断裂是复制依赖性的，发生在 G1 和 G2 期细胞中。当用活性氧物质清除剂 N-乙酰半胱氨酸处理细胞时，双链断裂减少，但这并没有挽救细胞增殖缺陷，表明需要 Rev3L 来耐受或修复几类内源性形成的 DNA 损伤。T 抗原使细胞永生化，从而允许细胞生长。总之，即使在没有外部 DNA 挑战的情况下，聚合酶 ζ 对于预防正常哺乳动物细胞的每个分裂中的复制依赖性 DNA 断裂也是必需的。在体内缓慢增殖的小鼠细胞中丢失聚合酶 ζ 可能会导致染色体畸变的积累，从而导致肿瘤发生。聚合酶 ζ 在 TLS 聚合酶中是独一无二的，因为它在细胞增殖中起着重要作用。
