Transcript regulation of human telomerase reverse transcriptase by c-myc and mad1.
Telomerase activity is highly positive correlated to most malignant neoplasms. Human telomerase reverse transcriptase (hTERT) is the rate-limiting factor of telomerase activity. Recent studies have shown that the expression of hTERT is mainly determined by its transcript regulation. Among the transcript regulation factors of hTERT, c-myc and mad1 are well known. Here, we constructed c-myc and mad1 eukaryotic expression vectors, then co-transfected them with the wild-type (Tw) or mutant hTERT promoter (Td) luciferase reporter plasmid, which were double-mutated in the E-box sequences from CACGTG to CACCTG of Tw. The change of luciferase activity in different cells was detected. The results showed that Tw was obviously activated in T24 and EJ bladder cancer cells, but not in normal fibrocytes. c-myc and mad1 had positive and negative effects respectively on the Tw transcript in a dose-dependent manner, while the roles of c-myc and mad1 in regulating the Td transcript were reversed. c-myc combined with mad1 can down-regulate Tw but not Td. These observations indicate that c-myc and mad1 can regulate the hTERT transcript in a different manner in hTERT positive cells, but not in normal cells. This may provide an insight into some telomerase-related carcinogenesis mechanisms.
Zou
Lin
L
Faculty of Laboratory Medicine, Chongqing University of Medical Sciences, Chongqing 400016, China.
Zhang
Peng-Hui
PH
Luo
Chun-Li
CL
Tu
Zhi-Guang
ZG
D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D017930:Genes, Reporter; D005822:Genetic Vectors; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism*; D014162:Transfection
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C501384:MAD1L1 protein, human; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D004247:DNA; D008156:Luciferases; D019098:Telomerase