title: Embryonic and adult isoforms of XLAP2 form microdomains associated with chromatin and the nuclear envelope.
abstract: Laminin-associated polypeptide 2 (LAP2) proteins are alternatively spliced products of a single gene; they belong to the LEM domain family and, in mammals, locate to the nuclear envelope (NE) and nuclear lamina. Isoforms lacking the transmembrane domain also locate to the nucleoplasm. We used new specific antibodies against the N-terminal domain of Xenopus LAP2 to perform immunoprecipitation, identification and localization studies during Xenopus development. By immunoprecipitation and mass spectrometry (LC/MS/MS), we identified the embryonic isoform XLAP2γ, which was downregulated during development similarly to XLAP2ω. Embryonic isoforms XLAP2ω and XLAP2γ were located in close association with chromatin up to the blastula stage. Later in development, both embryonic isoforms and the adult isoform XLAP2β were localized in a similar way at the NE. All isoforms colocalized with lamin B2/B3 during development, whereas XLAP2β was colocalized with lamin B2 and apparently with the F/G repeat nucleoporins throughout the cell cycle in adult tissues and culture cells. XLAP2β was localized in clusters on chromatin, both at the NE and inside the nucleus. Embryonic isoforms were also localized in clusters at the NE of oocytes. Our results suggest that XLAP2 isoforms participate in the maintenance and anchoring of chromatin domains to the NE and in the formation of lamin B microdomains.
authors.affiliation: Laboratory of Nuclear Proteins, Faculty of Biotechnology, University of Wrocław, Przybyszewskiego 63/77, 51-148, Wrocław, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Chmielewska
authors.forename: Magda
authors.initials: M
authors.lastname: Dubińska-Magiera
authors.forename: Mirosław
authors.initials: M
authors.lastname: Sopel
authors.forename: Dorota
authors.initials: D
authors.lastname: Rzepecka
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hutchison
authors.forename: Martin W
authors.initials: MW
authors.lastname: Goldberg
authors.forename: Ryszard
authors.initials: R
authors.lastname: Rzepecki
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D021962:Membrane Microdomains / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism* / Q000648:ultrastructure; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D020033:Protein Isoforms; C093413:lamina-associated polypeptide 2