The mouse homologue of hst/k-FGF: sequence, genome organization and location relative to int-2.

We have located and sequenced the murine homologue of the hst/k-FGF oncogene in genomic DNA clones that extend 3' from int-2 on mouse chromosome 7. The two genes are in the same transcriptional orientation, less than 20 kilobase pairs (kb) apart, and presumably evolved by tandem duplication of a common ancestral gene. RNase mapping and primer extension analyses indicated that the major 3.2 kb hst transcript expressed in undifferentiated embryonal carcinoma (EC) cell lines initiates at a unique cap site downstream from an obvious TATA-box. The 3' end of the transcript as identified in multiple cDNA clones occurs at an appropriate distance from a variant polyadenylation signal, ATTAAA. Translation of the major open reading frame would yield a 202 amino acid protein that is 82% homologous to human HST but lacking 4 residues at the presumed signal peptide cleavage site.