| Summary: | 碩士 === 國立臺灣大學 === 醫事技術學研究所 === 89 === Non-random DNA sequences which have the potential to adopt a number of unusual secondary structure often trigger or modulate important biological processes. DNA hairpins are thought to be involved in different systems such as activation, repression or termination of transcription and may interfere with DNA synthesis and/or cause instability. Hairpin structures have also been shown to be directly associated with various human diseases, such as fragile X syndrome, Huntington’s disease and myotonic dystrophy.
The methyl-directed mismatch repair system in Escherichia coli maintains genetic stability by correcting DNA biosynthetic errors and ensuring the fidelity of homologous genetic recombination. It is interesting to know whether a mismatch-containing hairpin could provoke the repair by E.coli mismatch repair system. To test this idea, we constructed a set of DNA heteroduplexes containing hairpin structure mispairs to characterize the in vitro reaction in Escherichia coli cell free extracts.
Our results showed the methyl-directed system could process these heterologies on the unmethylated strand. The reaction requires MutS, MutL, MutH, dNTPs and ATP. We also detected activities processing hairpin structures in a methylation independent manner, the activity was dependent on dNTPs but independent of E.coli mutHLS system and sbcCD gene products.
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