- 作者: Yi-Kuang Chuang; Wern-Cherng Cheng; Steven D. Goodman; Yu-Ting Chang; Jau-Tsuen Kao; Chun-Nan Lee; Keh-Sung Tsai; Woei-horng Fang
- 作者服務機構: 1 Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, 7, Chung-Shan South Road, Taipei, Taiwan, 100-63, ROC; ; 2 Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan, 100-63, ROC; ; 3 Division of Diagnostic Sciences, University of Southern California School of Dentistry, Los Angeles, California, 90089-0641, USA
- 中文摘要: --
- 英文摘要: Palindromic sequences present in DNA may form secondary structures that block DNA replication and transcription causing adverse effects on genome stability. It has been suggested that hairpin structures containing mispaired bases could stimulate the repair systems in human cells. In this study, processing of variable length of palindromic loops in the presence or absence of single-base mismatches was investigated in human cell extracts. Our results showed that hairpin structures were efficiently processed through a nick-directed mechanism. In a similar sequence context, mismatch-containing hairpins have higher repair efficiencies. We also found that shorter hairpins are generally better repaired. A strand break located either 3' or 5' to the loop is sufficient to activate hairpin repair on the nicked strand. The reaction requires Mg2+, the four dNTPs and hydrolysis of ATP for efficient repair on both palindromic loop insertions and deletions. Correction of each of these heteroduplexes was abolished by aphidicolin but was relatively insensitive to the presence of ddTTP, suggesting involvement of polymerase(s) α and/or δ. These findings are most consistent with the nick-directed loop repair pathway being responsible for processing hairpin heterologies in human cells.
- 中文關鍵字: --
- 英文關鍵字: DNA loop repair, human cells, mismatch repair, nick-directed, palindromic sequence