title: A new human dyskerin isoform with cytoplasmic localization.
abstract: BACKGROUND
  The human DKC1 gene is causative of X-linked dyskeratosis congenita (X-DC), a syndrome characterized by mucocutaneous features, bone marrow failure, tumor susceptibility, perturbation of stem cell function, and premature aging. DKC1 is thought to produce a single protein, named dyskerin, which shows strict nucleolar localization and participates in at least two distinct nuclear functional complexes: the H/ACA small nucleolar ribonucleoproteic complex involved in RNA pseudouridylation and the active telomerase complex.
  
  
  METHODS
  By bioinformatics and molecular analyses we identified a DKC1 splice variant able to encode a truncated form of dyskerin, confirmed its active expression in diverse human tissues by RT-PCR, and showed by immunoblotting and immunocytochemistry experiments that it actually encodes a novel protein. Stably transfected clones over-expressing the new isoform were analyzed for growth, morphology and adhesion properties.
  
  
  RESULTS
  Our results show that DKC1 encodes a new alternatively spliced mRNA able to direct the synthesis of a variant dyskerin with unexpected cytoplasmic localization. Intriguingly, when over-expressed in HeLa cells, the new isoform promotes cell to cell and cell to substratum adhesion, increases the cell proliferation rate and leads to cytokeratin hyper-expression.
  
  
  CONCLUSIONS
  Our results highlight a novel degree of complexity and regulation of the human DKC1 gene and reveal that it can play a further, unpredicted role in cell adhesion. The identification of a dyskerin cytoplasmic variant reinforces the view that other mechanisms, in addition to telomere instability, can significantly contribute to the pathogenesis of the X-DC, and suggests that DKC1 nucleolar and cytoplasmic functions might cumulatively account for the plethora of manifestations displayed by this syndrome.
authors.affiliation: Department of Structural and Functional Biology, University of Naples "Federico II", Complesso Universitaro Monte Santangelo, via Cinthia, 80216 Napoli. Italy. aangrisa@studenti.unina.it
authors.forename: Alberto
authors.initials: A
authors.lastname: Angrisani
authors.forename: Mimmo
authors.initials: M
authors.lastname: Turano
authors.forename: Lorella
authors.initials: L
authors.lastname: Paparo
authors.forename: Concetta
authors.initials: C
authors.lastname: Di Mauro
authors.forename: Maria
authors.initials: M
authors.lastname: Furia
mesh_terms: D017398:Alternative Splicing; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C112148:DKC1 protein, human; D009687:Nuclear Proteins; D020033:Protein Isoforms