title: β- and γ-Actins in the nucleus of human melanoma A375 cells.
abstract: Actin is a highly conserved protein that is expressed in all eukaryotic cells and has essential functions in the cytoplasm and the nucleus. Nuclear actin is involved in transcription by all three RNA polymerases, chromatin remodelling, RNA processing, intranuclear transport, nuclear export and in maintenance of the nuclear architecture. The nuclear actin level and polymerization state are important factors regulating nuclear processes such as transcription. Our study shows that, in contrast to the cytoplasm, the majority of endogenous nuclear actin is unpolymerized in human melanoma A375 cells. Most mammalian cells express the two non-muscle β- and γ-actin isoforms that differ in only four amino acids. Despite their sequence similarity, studies analysing the cytoplasmic functions of these isoforms demonstrated that β- and γ-actins show differences in localization and function. However, little is known about the involvement of the individual actin isoforms in nuclear processes. Here, we used the human melanoma A375 cell line to analyse actin isoforms in regard to their nuclear localization. We show that both β- and γ-non-muscle actin isoforms are present in nuclei of these cells. Immunolocalization studies demonstrate that both isoforms co-localize with RNA polymerase II and hnRNP U. However, we observe differences in the ratio of cytoplasmic to nuclear actin distribution between the isoforms. We show that β-actin has a significantly higher nucleus-to-cytoplasm ratio than γ-actin.
authors.affiliation: Department of Animal Developmental Biology, Institute of Experimental Biology, Faculty of Biological Sciences, University of Wroclaw, Sienkiewicza 21, 50-335, Wroclaw, Poland. marta.migocka-patrzalek@uwr.edu.pl.|Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland. marta.migocka-patrzalek@uwr.edu.pl.|Department of Physiology and Biophysics, University at Buffalo State University of New York, Buffalo, NY, USA. marta.migocka-patrzalek@uwr.edu.pl.
authors.forename: Marta
authors.initials: M
authors.lastname: Migocka-Patrzałek
authors.affiliation: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Makowiecka
authors.affiliation: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Nowak
authors.affiliation: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Antonina J
authors.initials: AJ
authors.lastname: Mazur
authors.affiliation: Department of Physiology and Biophysics, University at Buffalo State University of New York, Buffalo, NY, USA.
authors.forename: Wilma A
authors.initials: WA
authors.lastname: Hofmann
authors.affiliation: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Malicka-Błaszkiewicz
mesh_terms: D000199:Actins / Q000032:analysis / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008545:Melanoma / Q000378:metabolism / Q000473:pathology*; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000199:Actins; D020033:Protein Isoforms
keywords: Actin; Actin isoform; Actin polymerization state; Nuclear actin; Nucleus