title: Lamin misexpression upregulates three distinct ubiquitin ligase systems that degrade ATR kinase in HeLa cells.
abstract: Lamins are the major structural components of the nucleus and mutations in the human lamin A gene cause a number of genetic diseases collectively termed laminopathies. At the cellular level, lamin A mutations cause aberrant nuclear morphology and defects in nuclear functions such as the response to DNA damage. We have investigated the mechanism of depletion of a key damage sensor, ATR (Ataxia-telangiectasia-mutated-and-Rad3-related) kinase, in HeLa cells expressing lamin A mutants or lamin A shRNA. The degradation of ATR kinase in these cells was through the proteasomal pathway as it was reversed by the proteasomal inhibitor MG132. Expression of lamin A mutants or shRNA led to transcriptional activation of three ubiquitin ligase components, namely, RNF123 (ring finger protein 123), HECW2 (HECT domain ligase W2) and the F-box protein FBXW10. Ectopic expression of RNF123, HECW2 or FBXW10 directly resulted in proteasomal degradation of ATR kinase and the ring domain of RNF123 was required for this degradation. However, these ligases did not alter the stability of DNA-dependent protein kinase, which is not depleted upon lamin misexpression. Although degradation of ATR kinase was reversed by MG132, it was not affected by the nuclear export inhibitor, leptomycin B, suggesting that ATR kinase is degraded within the nucleus. Our findings indicate that lamin misexpression can lead to deleterious effects on the stability of the key DNA damage sensor, ATR kinase by upregulation of specific components of the ubiquitination pathway.
authors.affiliation: Centre for Cellular and Molecular Biology (CSIR), Uppal Road, Hyderabad 500007, India.
authors.forename: Bhattiprolu
authors.initials: B
authors.lastname: Muralikrishna
authors.forename: Pankaj
authors.initials: P
authors.lastname: Chaturvedi
authors.forename: Kirti
authors.initials: K
authors.lastname: Sinha
authors.forename: Veena K
authors.initials: VK
authors.lastname: Parnaik
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D034904:Lamin Type A / Q000235:genetics* / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011489:Protein Denaturation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D018797:Cell Cycle Proteins; D044783:F-Box Proteins; C574378:FBXW10 protein, human; D034904:Lamin Type A; D007976:Leupeptins; D061988:Proteasome Inhibitors; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C574377:HECW2 protein, human; C574376:RNF123 protein, human; D044767:Ubiquitin-Protein Ligases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde