MOLECULAR CLONING OF hTRT CATALYTIC DOMAIN FROM HeLa CELLS AND ITS EXPRESSION IN E. Coli AND PURIFICATION

Objective. To investigate the expression of telomemse genc hTRT mRNA in HeLa cells and to obtain hTRT pro-tein for luther study. Methods. The genc for encoding hTRT catalytic domain was cloned based on RT-PCR amplification from HeLa cells and sequenced. The cloned hTRTcDNA was in-frame inserted into His-tag fusion expression vector pEK318. The His-tag hTRT fusion proteins were purified by Ni-NTA chromatography and stained by western blotting. Results. An approximately 620bp fragment was generated and cloned into pBluescfipt SK + between Sall and BamHI sites. DNA sequencing showed the isolated fragment was consistent to those reported. SDS-PAGE present that a 17kDa protein was expressed stably in E.coli JM109 harboring pEKTRT344 containing 6 × His-tag and hTRT 150aa, and the expression level of the protein was about 26% of the total bacterial proteins, while the expression of pEKTRT containing 6 × His-tag and hTRT 243aa was only detectable as 27 kDa hand in western blotting. Both of fu-sion proteins were purified by Ni-NTA chromatography and showed single band( > 95% pufifity) in Coomassie Bril-liant staining. Western-blotting confmned that two proteins could be recognized by the Ni-NTA AP conjugate. Conclusions. The hTRT catalytic domain was highly conserved. The expressed hTRT protein contained recogniz-able His-tag, telomerase-specific and strong antigenic epitops, which may be convenient for ftrrther investigation.