Functional studies of DNA repair genes hHR23A and hHR23B

• Main Authors: Hui-Chuan Hsieh, 謝惠娟
• Other Authors: Wenya Huang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/86905455926607956980

碩士 === 國立成功大學 === 醫學工程研究所碩博士班 === 92 === DNA repair is an essential mechanism for cellular defense to mutations and cancers. This project studies the functions of human DNA repair genes hHR23A and hHR23B. The human hHR23A and hHR23B genes are two sequence homologues of the Saccharomyces cerevisiae rad23 gene. These two factors both contain a few functional domains, including an ubiquitin-like (UBL) domain at the N-termini, two ubiquitin-associated (UBA) domains and an XPC-binding domain. Previous studies showed that the hHR23B protein is complexed with the XP group C (XPC) protein, defective in the xeroderma pigmentosum C syndrome, and is involved in the global genome nucleotide excision repair (NER) pathway. Therefore, the hHR23B is involved in NER. However, the function of hHR23A is not clear so far. To study the functions of hHR23A and B, we have employed the RNA interference (RNAi) techniques to construct the knock-down (KD) models for these two genes. The hHR23Ai and hHR23Bi constructs could reduce endogenous levels of the hHR23A or hHR23B in HtTA1 cells by around 50%. Either of the hHR23A or B KD cells were more sensitive to UV irradiation than the wild type cells were. By the host reactivation assay as well as the South-western blot to observe DNA repair activities in the hHR23A/B KD cells, we found that the hHR23A and B are required for NER. By co-immunoprecipitation analysis, we also found that NER activator GADD45�� protein interacts with the hHR23A, indicating that the hHR23A is associated with the GADD45A in vivo. Other study in the lab also found that the hHR23A is associated with the tumor suppressor p53 protein. In conclusion, the hHR23A and hHR23B proteins are NER factors in vivo. And the fact that the hHR23A is associated with GADD45A suggests that the hHR23A is a NER factor and performs its functional role in concert with GADD45A and p53.