Actin is a highly conserved protein that polymerizes to produce filaments that form cross-linked networks in the cytoplasm of cells. Actin exists in both monomeric (G-actin) and polymeric (F-actin) forms, both forms playing key functions, such as cell motility and contraction. In addition to their role in the cytoplasmic cytoskeleton, G- and F-actin also localize in the nucleus, and regulate gene transcription and motility and repair of damaged DNA. Polymerization of globular actin (G-actin) leads to a structural filament (F-actin) in the form of a two-stranded helix. Each actin can bind to 4 others. Identified in a IGF2BP1-dependent mRNP granule complex containing untranslated mRNAs. Component of the BAF complex, which includes at least actin (ACTB), ARID1A, ARID1B/BAF250, SMARCA2, SMARCA4/BRG1, ACTL6A/BAF53, ACTL6B/BAF53B, SMARCE1/BAF57 SMARCC1/BAF155, SMARCC2/BAF170, SMARCB1/SNF5/INI1, and one or more of SMARCD1/BAF60A, SMARCD2/BAF60B, or SMARCD3/BAF60C. In muscle cells, the BAF complex also contains DPF3. Found in a complex with XPO6, Ran, ACTB and PFN1. Interacts with XPO6 and EMD. Interacts with ERBB2. Interacts with GCSAM (By similarity). Interacts with TBC1D21. Interacts with CPNE1 (via VWFA domain) and CPNE4 (via VWFA domain) (By similarity). Interacts with DHX9 (via C-terminus); this interaction is direct and mediates the attachment to nuclear ribonucleoprotein complexes. Interacts with FAM107A (By similarity). Localized in cytoplasmic mRNP granules containing untranslated mRNAs. ISGylated. Oxidation of Met-29 and Met-32 by MICALs (MICAL1, MICAL2 or MICAL3) to form methionine sulfoxide promotes actin filament depolymerization. MICAL1 and MICAL2 produce the (R)-S-oxide form. The (R)-S-oxide form is reverted by MSRB1 and MSRB2, which promote actin repolymerization. Monomethylation at Lys-69 (K84me1) regulates actin-myosin interaction and actomyosin-dependent processes. Demethylation by ALKBH4 is required for maintaining actomyosin dynamics supporting normal cleavage furrow ingression during cytokinesis and cell migration. Actin, cytoplasmic 1, N-terminally processed: N-terminal acetylation by NAA80 affects actin filament depolymerization and elongation, including elongation driven by formins. In contrast, filament nucleation by the Arp2/3 complex is not affected. Methylated at His-58 by SETD3 (By similarity). Methylation at His-73 is required for smooth muscle contraction of the laboring uterus during delivery (By similarity). In vertebrates 3 main groups of actin isoforms, alpha, beta and gamma have been identified. The alpha actins are found in muscle tissues and are a major constituent of the contractile apparatus. The beta and gamma actins coexist in most cell types as components of the cytoskeleton and as mediators of internal cell motility. Belongs to the actin family.