IDENTIFICATION OF AN EFS ISOFORM THAT LACKS THE SH3 DOMAIN AND CHROMOSOMAL MAPPING OF HUMAN EFS

Efs was originally found by expression cloning of a mouse embryo cDNA library through its Fyn-SH3 binding capacity (Ishino et al., Oncogene 11, 2331-2338, 1995), Efs has characteristic regions important in intr acellular signal transduction; these are an SH3 domain, a cluster of p utative ligands for SH2 domains and proline-rich sequences with SH3-bi nding consensus, In this paper, we report cDNA cloning of human Efs an d a variant of it from a hippocampal cDNA library, The human Efs gene was mapped to chromosome 14q11.2-q12 by fluorescence in situ hybridiza tion. We identified two forms of human Efs, designated hEfs1 and hEfs2 , hEfs1 represents the human counterpart of original mouse embryo Efs (mEfs1), hEfs2, the newly identified form, is identical to hEfs1, exce pt for its lack of the SH3 domain, hEfs1 and mEfs1 are 80% identical i n their amino acid sequences and 100% identical within the SH3 domain. Reverse transcription polymerase chain reaction analysis of adult mou se tissue RNA indicated expression of Efs2 and of Efs1 in various tiss ues, Evidence suggesting the presence of the Efs2 protein in human tis sue was obtained by immunoprecipitation followed by immunoblotting wit h two different anti-Efs antibodies. Possible functions of Efs2 are di scussed.