| Summary: | 碩士 === 國立陽明大學 === 醫學生物技術研究所 === 95 === It is well-known that methylation status of CpG island in the promoter and/or regulation region may alter transcriptional activities of the down-streamed genes. However, these E. coli hosts may equip different DNA methylation activities. For instance, E. coli JM109 and DH5α contain Dam and Dcm methylase; E. coli JM110, GM 2163 lose both activities. It has not been documented whether plasmids with different E. coli methylation alter their expression or cis-reporting activities in mammalian cells when transient transfection is conducted. In this report, cis-reporting plasmids were tested. When promoter/enhancer of tested plasmids contained several Dam/Dcm sites, the cis-reporting activity was 2-4 folds lower for those plasmids isolated from JM109 than from JM110. However, the ectopic E. coli methylations had little effect on transcription if the methylations happened in the coding region. These findings suggest that cis-reporting plasmids used in comparative or successive experiments had better be derived from E. coli strain with same methylase status. Plasmid for promoter-transcription factor association studies is suggested to use Dam/Dcm negative E. coli strains.
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