Expression of the CTCF-paralogous cancer-testis gene, brother of the regulator of imprinted sites (BORIS), is regulated by three alternative promoters modulated by CpG methylation and by CTCF and p53 transcription factors.
BORIS, like other members of the 'cancer/testis antigen' family, is normally expressed in testicular germ cells and repressed in somatic cells, but is aberrantly activated in cancers. To understand regulatory mechanisms governing human BORIS expression, we characterized its 5'-flanking region. Using 5' RACE, we identified three promoters, designated A, B and C, corresponding to transcription start sites at -1447, -899 and -658 bp upstream of the first ATG. Alternative promoter usage generated at least five alternatively spliced BORIS mRNAs with different half-lives determined by varying 5'-UTRs. In normal testis, BORIS is transcribed from all three promoters, but 84% of the 30 cancer cell lines tested used only promoter(s) A and/or C while the others utilized primarily promoters B and C. The differences in promoter usage between normal and cancer cells suggested that they were subject to differential regulation. We found that DNA methylation and functional p53 contributes to the negative regulation of each promoter. Moreover, reduction of CTCF in normally BORIS-negative human fibroblasts resulted in derepression of BORIS promoters. These results provide a mechanistic basis for understanding cancer-related associations between haploinsufficiency of CTCF and BORIS derepression, and between the lack of functional p53 and aberrant activation of BORIS.
Renaud
Stéphanie
S
Section of Molecular Pathology, Laboratory of Immunopathology, NIAID, NIH, Rockville, MD 20815, USA.
Pugacheva
Elena M
EM
Delgado
M Dolores
MD
Braunschweig
Richard
R
Abdullaev
Ziedulla
Z
Loukinov
Dmitri
D
Benhattar
Jean
J
Lobanenkov
Victor
V
D020121:5' Untranslated Regions / Q000032:analysis; D017398:Alternative Splicing; D001483:Base Sequence; D000076246:CCCTC-Binding Factor; D002460:Cell Line; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000235:genetics; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D020121:5' Untranslated Regions; D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; C456540:CTCFL protein, human; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53