FNBP1, FNBP1L, CIP4/TRIP10, FNBP2, SRGAP1/ARHGAP13, SRGAP2/ARHGAP14, ARHGAP4, FCHSD1, and FCHSD2 constitute the FCFBS superfamily characterized by FES-CIP4 homology (FCH) domain, Formin-binding FNBP1-FNBP2 homology (FBH) domain, and SRC homology 3 (SH3) domain. During genome-wide searching for human genes encoding FCH domain molecules, we identified the FCHO2 gene by using bioinformatics. DKFZp451B033 (AL831971.1) was the representative cDNA derived from human FCHO2 gene, while FLJ32208 (AK056770.1) was a chimeric cDNA generated by the recombination between FCHO2 and CSH1 genes. MGC63242 (BC052456.1) rather than 5832424M12 (AK031041.1) was the representative cDNA derived from mouse Fcho2 gene. FCHO2 gene, consisting of 26 exons, was mapped to human chromosome 5q13.2. Human FCHO2 (810 aa) showed 94.6% total-amino-acid identity with mouse Fcho2 (809 aa), and 50.4% total-amino-acid identity with human FCHO1. Drosophila CG8176 (NP_788613.1) and C. elegans 2B609 (NP_493947.1) were homologs of mammalian FCHO2 and FCHO1. FCHO-homologous (FOH) domain (codon 527-810 of human FCHO2) was identified as the novel domain conserved among FCHO homologs. Human FCHO2, FCHO1, Drosophila CG8176 and C. elegans 2B609 were found consisting of N-terminal FCH domain and C-terminal FOH domain. This is the first report on identification and characterization of evolutionarily conserved FCHO homologs as well as the novel FOH domain.

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