Myb proteins suppress cytoskeletal reorganization by v-rel. Primary chicken embryo fibroblasts (CEF) and cells infected with the indicated viruses were stained with fluorescent phalloidin to decorate intracellular actin filaments. The cells infected with the Rel-ER virus showed a loss of actin cables and increased cortical actin in the presence of estrogen (+E2). Estrogen alone had no detectable effect on uninfected cells. Co-expression of c-myb (Rel-ERICB) suppressed this cytoskeletal reorganization.