Regulates actin polymerization by stimulating the actin-nucleating activity of the Arp2/3 complex (PubMed:16767080, PubMed:19366662, PubMed:19487689, PubMed:22847007, PubMed:22921828, PubMed:9422512). Involved in various processes, such as mitosis and cytokinesis, via its role in the regulation of actin polymerization (PubMed:19366662, PubMed:19487689, PubMed:22847007, PubMed:22921828, PubMed:9422512). Together with CDC42, involved in the extension and maintenance of the formation of thin, actin-rich surface projections called filopodia (PubMed:9422512). In addition to its role in the cytoplasm, also plays a role in the nucleus by regulating gene transcription, probably by promoting nuclear actin polymerization (PubMed:16767080). Binds to HSF1/HSTF1 and forms a complex on heat shock promoter elements (HSE) that negatively regulates HSP90 expression (By similarity). Plays a role in dendrite spine morphogenesis (By similarity). Decreasing levels of DNMBP (using antisense RNA) alters apical junction morphology in cultured enterocytes, junctions curve instead of being nearly linear (PubMed:19767742).
