Identification and characterization of negative regulatory elements of the human telomerase catalytic subunit (hTERT) gene promoter: possible role of MZF-2 in transcriptional repression of hTERT.
Human telomerase reverse transcriptase (hTERT) is a catalytic subunit of human telomerase and is a critical determinant of the enzymatic activity of telomerase. Expression of hTERT is known to be regulated mainly at the transcriptional level. In the present study, using transient expression assays, we identified a 400 bp silencer of the hTERT promoter between -776 and -378 upstream of the proximal core promoter. The inhibitory effects of this silencer were enhanced with cellular differentiation. A computer-assisted homology search identified multiple binding motifs for myeloid-specific zinc finger protein 2 (MZF-2) within this region. Mutation introduced in these sites resulted in significant activation of hTERT transcription. Gel shift assays demonstrated that MZF-2 proteins specifically bound to these sites. Overexpression of MZF-2 in cells led to down-regulation of hTERT transcription as well as telomerase activity. These findings suggest that the 400 bp region upstream of the hTERT core promoter that we identified functions as a negative regulatory region and that MZF-2 may be an effector of negative regulation of hTERT.
Fujimoto
K
K
Department of Molecular and Cellular Biology, Kanazawa University, Cancer Research Institute, School of Medicine, Japan.
Kyo
S
S
Takakura
M
M
Kanaya
T
T
Kitagawa
Y
Y
Itoh
H
H
Takahashi
M
M
Inoue
M
M
D001483:Base Sequence; D001665:Binding Sites; D020134:Catalytic Domain / Q000235:genetics*; D002454:Cell Differentiation; D016384:Consensus Sequence / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D020868:Gene Silencing; D006801:Humans; D051741:Kruppel-Like Transcription Factors; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012313:RNA; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D051741:Kruppel-Like Transcription Factors; C085969:MZF1 protein, human; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; C422952:telomerase RNA; D012313:RNA; D004247:DNA; D019098:Telomerase