The mammalian formin homology domain containing protein FHOD1 influences a variety of cellular events including cell migration, cytoskeletal arrangement, signal transduction, and gene expression. In this paper, we show that Src regulates a variety of FHODI-associated effects. FHOD1 distribution to lamellipodia was prevented by the absence of Src. However, stress fiber formation induced by a C-terminal truncated form of FHOD1 was unaffected. Gene expression from an SRE-dependent promoter and from the skeletal actin promoter was induced by two truncated forms of FHOD1 and in both instances, inhibition of Src tyrosine kinase activity abrogated induction of gene expression. Furthermore, Src activity was necessary to maintain mRNA levels of FHOD1 itself, and as such, this finding represents the first description of mechanisms involved in the regulation of formin gene expression in mammals. In summary, we have identified Src as a key regulator of FHOD1 biology. (c) 2005 Elsevier Inc. All rights reserved.