title: Cellular stress stimulates nuclear localization signal (NLS) independent nuclear transport of MRJ.
abstract: HSP40 family member MRJ (DNAJB6) has been in the spot light for its relevance to Huntington's, Parkinson's diseases, limb-girdle muscular dystrophy, placental development, neural stem cells, cell cycle and malignancies such as breast cancer and melanoma. This gene has two spliced variants coding for 2 distinct proteins with significant homology. However, MRJ(L) (large variant) is predominantly localized to the nucleus whereas MRJ(S) (small variant) is predominantly cytoplasmic. Interestingly MRJ(S) translocates to the nucleus in response to heat shock. The classical heat shock proteins respond to crises (stress) by increasing the number of molecules, usually by transcriptional up-regulation. Our studies imply that a quick increase in the molar concentration of MRJ in the nuclear compartment is a novel method by which MRJ responds to stress. We found that MRJ(S) shows NLS (nuclear localization signal) independent nuclear localization in response to heat shock and hypoxia. The specificity of this response is realized due to lack of such response by MRJ(S) when challenged by other stressors, such as some cytokines or UV light. Deletion analysis has allowed us to narrow down on a 20 amino acid stretch at the C-terminal region of MRJ(S) as a potential stress sensing region. Functional studies indicated that constitutive nuclear localization of MRJ(S) promoted attributes of malignancy such as proliferation and invasiveness overall indicating distinct phenotypic characteristics of nuclear MRJ(S).
authors.affiliation: Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA.
authors.forename: Joel F
authors.initials: JF
authors.lastname: Andrews
authors.forename: Landon J
authors.initials: LJ
authors.lastname: Sykora
authors.forename: Tiasha Barik
authors.initials: TB
authors.lastname: Letostak
authors.forename: Mitchell E
authors.initials: ME
authors.lastname: Menezes
authors.forename: Aparna
authors.initials: A
authors.lastname: Mitra
authors.forename: Sailen
authors.initials: S
authors.lastname: Barik
authors.forename: Lalita A
authors.initials: LA
authors.lastname: Shevde
authors.forename: Rajeev S
authors.initials: RS
authors.lastname: Samant
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D019556:COS Cells; D015687:Cell Hypoxia; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D018869:Heat-Shock Response; D006801:Humans; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: C485565:DNAJB6 protein, human; D050956:HSP40 Heat-Shock Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D019913:Nuclear Localization Signals; D020033:Protein Isoforms