Differential expression of two homologous and clustered oncogenes, Hst1 and Int-2, during differentiation of F9 cells.

HST1 (or HSTF1 in human gene nomenclature) transforming gene encodes a novel heparin-binding growth factor which has 40-50% homology with fibroblast growth factors and mouse Int-2 protein. Expression of mouse Hst1 or Int-2 is rare in adult tissues, but both of them are transcribed in embryos. We found that mouse Hst1 and Int-2, like their human counterparts, were located close to each other on the genome: the distance was less than 20 kbp. Hst1 was expressed in an undifferentiated mouse teratocarcinoma cell line, F9. Upon induction of differentiation of F9 cells, the amount of Hst1 transcript was markedly decreased, while that of Int-2 transcripts increased concomitantly.