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.