The tumor suppressor gene hypermethylated in cancer 1 is transcriptionally regulated by E2F1.
The Hypermethylated in Cancer 1 (HIC1) gene encodes a zinc finger transcriptional repressor that cooperates with p53 to suppress cancer development. We and others recently showed that HIC1 is a transcriptional target of p53. To identify additional transcriptional regulators of HIC1, we screened a set of transcription factors for regulation of a human HIC1 promoter reporter. We found that E2F1 strongly activates the full-length HIC1 promoter reporter. Promoter deletions and mutations identified two E2F responsive elements in the HIC1 core promoter region. Moreover, in vivo binding of E2F1 to the HIC1 promoter was shown by chromatin immunoprecipitation assays in human TIG3 fibroblasts expressing tamoxifen-activated E2F1. In agreement, activation of E2F1 in TIG3-E2F1 cells markedly increased HIC1 expression. Interestingly, expression of E2F1 in the p53(-/-) hepatocellular carcinoma cell line Hep3B led to an increase of endogenous HIC1 mRNA, although bisulfite genomic sequencing of the HIC1 promoter revealed that the region bearing the two E2F1 binding sites is hypermethylated. In addition, endogenous E2F1 induced by etoposide treatment bound to the HIC1 promoter. Moreover, inhibition of E2F1 strongly reduced the expression of etoposide-induced HIC1. In conclusion, we identified HIC1 as novel E2F1 transcriptional target in DNA damage responses.
Jenal
Mathias
M
Department of Clinical Research, University of Bern, Switzerland.
Trinh
Emmanuelle
E
Britschgi
Christian
C
Britschgi
Adrian
A
Roh
Vincent
V
Vorburger
Stephan A
SA
Tobler
Andreas
A
Leprince
Dominique
D
Fey
Martin F
MF
Helin
Kristian
K
Tschan
Mario P
MP
D001483:Base Sequence; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation; D050687:E2F1 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000187:drug effects
D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C499808:HIC1 protein, human; D051741:Kruppel-Like Transcription Factors; D012333:RNA, Messenger; D005047:Etoposide