Role of positive and negative regulation in modulation of the Fer promoter activity

Intronic promoter drives the BORIS-regulated expression of FerT in colon carcinoma cells

Fer is an intracellular tyrosine kinase that accumulates in most mammalian tissues. A truncated variant of Fer, FerT, is uniquely detected in spermatogenic cells and is absent from normal somatic tissues. Here, we show that in addition to Fer, FerT also accumulates in CC cells and in metastases derived from colorectal tumors, but not in normal human cells. Thus, FerT is a new member of the CTA protein family. Transcription of the ferT gene in CC cells was found to be driven by an intronic promoter residing in intron 10 of the fer gene and to be regulated by another CTA, the Brother of the Regulator of Imprinted Sites (BORIS) transcription factor. BORIS binds to the ferT promoter and down-regulation of BORIS significantly decreases the expression of ferT in CC cells. Accumulation of the ferT RNA was also regulated by the DNA methylation status and paralleled the expression profile of the boris transcript. Accordingly, the intronic ferT promoter was found to be hypomethylated in cancer cells expressing the FerT protein, by comparison with non-expressers. Collectively, we show here that FerT is a new CTA whose accumulation in CC cells, commonly considered low CTA expressers, is controlled by a novel transcription regulatory mechanism.