Formin homology proteins are actin regulators with scaffold function, which are implicated in organogenesis, normal tissue homeostasis, and cancer-cell invasion. FHOD1/FHOS, GRID2IP, Fmn1 and Fmn2 are non-FDD-type Formin homology proteins, while FMNL1, FMNL2/FHOD2, FMNL3, DAAM1, DAAM2, DIAPH1, DIAPH2 and DIAPH3 are FDD-type Formin homology proteins. Here, we identified and characterized FHOD3 (also known as FHOS2), a novel gene homologous to FHOD1, by using bioinformatics. Because FLJ46173, FLJ22297, KIAA1695 and FLJ34580 were partial FHOD3 cDNAs, complete coding sequence of FHOD3 cDNA was determined by assembling nucleotide sequences of FLJ46173 and FLJ22297. FHOD3 gene at human chromosome 18q12.2 was found consisting of at least 25 exons. Exon 11 of FHOD3 gene was spliced out in KIAA1695 cDNA and BF116064 EST, while exon 13 of FHOD3 gene was spliced out in FLJ46173 cDNA. FHOD3 gene encodes at least three isoforms due to alternative splicing of the exon skipping type. FHOD3 and FHOD1 showed 52.1% total-amino-acid identity. Drosophila CG32030 showed 43.9% total-amino-acid identity with human FHOD3, and 39.1% total-amino-acid identity with human FHOD1. FHDHN domain (codon 1-327 of FHOD3) and FHDHC domain (codon 1377-1421 of FHOD3) were identified as the N-terminal conserved region and the juxta C-terminal conserved region, respectively. Human FHOD3, FHOD1 and Drosophila CG32030 were found to share the conserved domain structure consisting of FHDHN, FH1, FH2, and FHDHC domains. This is the first report on the FHOD3 gene as well as on the novel FHDHN and FHDHC domains.

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