Wani Manzoor A, El-Mahdy Mohammed A, Hamada Farid M, Wani Gulzar, Zhu Qianzheng, Wang Qi-en, Wani Altaf A
Department of Radiology, The Ohio State University, Columbus 43210, USA.
Mutat Res. 2002 Aug 29;505(1-2):13-25. doi: 10.1016/s0027-5107(02)00107-0.
Wild-type p53 protein is known to regulate the global genomic repair (GGR), removing bulky chemical DNA adducts as well as cyclobutane pyrimidine dimers from the genome overall and from non-transcribed strands (NTS) in DNA. To investigate the role of cellular factor(s) relevant to p53 regulated DNA repair processes, we examined the repair kinetics of chemical carcinogen, anti-benzo[a]pyrene-diol epoxide (anti-BPDE), induced bulky DNA adducts in normal human mammary epithelial cells (HMECs) and HMEC transformed by human papillomavirus (HPV)-16E6 or -16E7 oncoproteins, which, respectively targets p53 or pRb proteins for degradation. The results show that the removal of anti-BPDE DNA adducts from the genome overall and NTS by GGR was significantly reduced in HPV-16E6 protein expressing cells as compared to that in normal and HPV-16E7 protein expressing cells, indicating the role of p53 and not pRb in nucleotide excision repair (NER). We further determined the potential effects of the p53-regulated p21(waf1/cip1) gene product in NER in human colon carcinoma, HCT116 cells expressing wild-type p53 but different p21(waf1/cip1) genotypes (p21+/+, p21+/-, p21-/-). The results donot show a discernible difference in the removal of anti-BPDE DNA adducts from the genome overall and the transcribed strand (TS) and NTS irrespective of the presence or absence of p21(waf1/cip1) expression. Based on these results, we suggest that: (i) the wild-type p53 function but not p21(waf1/cip1) expression is necessary for GGR of chemical induced bulky DNA adducts; (ii) the Rb gene product does not play a significant role in NER; and (iii) the modulation of NER by p53 may be independent of its function in the regulation of cell cycle arrest upon chemically induced DNA damage.
已知野生型p53蛋白可调节全基因组修复（GGR），从整个基因组以及DNA的非转录链（NTS）中去除大量化学性DNA加合物以及环丁烷嘧啶二聚体。为了研究与p53调控的DNA修复过程相关的细胞因子的作用，我们检测了化学致癌物反式苯并[a]芘二醇环氧化物（anti-BPDE）诱导的大量DNA加合物在正常人乳腺上皮细胞（HMECs）以及由人乳头瘤病毒（HPV）-16E6或-16E7癌蛋白转化的HMEC中的修复动力学，HPV-16E6或-16E7癌蛋白分别靶向p53或pRb蛋白进行降解。结果显示，与正常细胞和表达HPV-16E7蛋白的细胞相比，在表达HPV-16E6蛋白的细胞中，GGR从整个基因组和NTS中去除anti-BPDE DNA加合物的能力显著降低，这表明p53而非pRb在核苷酸切除修复（NER）中发挥作用。我们进一步确定了p53调控的p21（waf1/cip1）基因产物在人结肠癌HCT116细胞NER中的潜在作用，这些细胞表达野生型p53但具有不同的p21（waf1/cip1）基因型（p21+/+、p21+/-、p21-/-）。结果表明，无论p21（waf1/cip1）是否表达，从整个基因组、转录链（TS）和NTS中去除anti-BPDE DNA加合物均无明显差异。基于这些结果，我们认为：（i）化学诱导的大量DNA加合物的GGR需要野生型p53功能而非p21（waf1/cip1）表达；（ii）Rb基因产物在NER中不发挥重要作用；（iii）p53对NER的调节可能独立于其在化学诱导的DNA损伤后调控细胞周期停滞中的功能。
