Colon Cancer-associated DNA Polymerase β Variant Induces Genomic Instability and Cellular Transformation
Colon Cancer-associated DNA Polymerase β Variant Induces Genomic Instability and Cellular Transformation
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DOI：
10.1074/jbc.m112.362111
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发表时间：
2012-07-06
影响因子：
4.8
通讯作者：
Sweasy, Joann B.
中科院分区：
文献类型：
--
作者：
Nemec, Antonia A.;Donigan, Katherine A.;Sweasy, Joann B.
快速发展的技术已经产生了几种人类肿瘤的基因组序列。我们已经在人类结直肠癌中发现了 DNA 聚合酶 β (pol β) 基因的几种突变。我们已经证明 pol beta G231D 变体的表达会增加染色体畸变并诱导细胞转化。即使 G231D 的表达消失，转化的表型仍会在细胞中持续存在，这表明这是基因组不稳定的结果。生化分析表明其催化速率比WTpol beta慢140倍，这是G231D降低核苷酸结合亲和力的结果。 pol beta 的残基 231 非常靠近 DNA 的模板链。分子模型表明，从小的非极性甘氨酸到带负电的天冬氨酸的变化导致模板和残基 231 之间的排斥，导致 dNTP 结合袋变形。此外，G231D的表达不足以挽救用化疗药物治疗的pol β缺陷细胞，这表明这些药物可以有效地用于治疗携带这种突变的肿瘤。更重要的是，这表明 G231D 变体损害了碱基切除修复。总之，这些数据表明 G231D 变体在促进癌症方面发挥着作用。
Rapidly advancing technology has resulted in the generation of the genomic sequences of several human tumors. We have identified several mutations of the DNA polymerase beta (pol beta) gene in human colorectal cancer. We have demonstrated that the expression of the pol beta G231D variant increased chromosomal aberrations and induced cellular transformation. The transformed phenotype persisted in the cells even once the expression of G231D was extinguished, suggesting that it resulted as a consequence of genomic instability. Biochemical analysis revealed that its catalytic rate was 140-fold slower than WTpol beta, and this was a result of the decreased binding affinity of nucleotides by G231D. Residue 231 of pol beta lies in close proximity to the template strand of the DNA. Molecular modeling demonstrated that the change from a small and nonpolar glycine to a negatively charged aspartate resulted in a repulsion between the template and residue 231 leading to the distortion of the dNTP binding pocket. In addition, expression of G231D was insufficient to rescue pol beta-deficient cells treated with chemotherapeutic agents suggesting that these agents may be effectively used to treat tumors harboring this mutation. More importantly, this suggests that the G231D variant has impaired base excision repair. Together, these data indicate that the G231D variant plays a role in driving cancer.