E3 ubiquitin ligase HECW2 targets PCNA and lamin B1

• Published in: Biochimica et biophysica acta. Molecular cell research 2018-08, Vol.1865 (8), p.1088-1104
• Main Authors: Krishnamoorthy, Vidhya, Khanna, Richa, Parnaik, Veena K.
• Format: Article
• Language: English
• Subjects: Binding Sites; E3 ligase HECW2; HEK293 Cells; Humans; Lamin A/C; Lamin B1; Lamin Type A - genetics; Lamin Type B - chemistry; Lamin Type B - genetics; Lamin Type B - metabolism; Laminopathies; Muscular Dystrophy, Emery-Dreifuss - genetics; Mutation; PCNA; Proliferating Cell Nuclear Antigen - chemistry; Proliferating Cell Nuclear Antigen - metabolism; Proteasomal degradation; Proteasome Endopeptidase Complex - chemistry; Proteasome Endopeptidase Complex - metabolism; Proteolysis; Ubiquitin-Protein Ligases - chemistry; Ubiquitin-Protein Ligases - metabolism; Ubiquitination
• ISSN: 0167-4889; 1879-2596
• DOI: 10.1016/j.bbamcr.2018.05.008

Lamins constitute the major architectural proteins of the nuclear lamina that help in maintaining nuclear organization. Mutations in lamins are associated with diverse degenerative diseases, collectively termed laminopathies. HECW2, a HECT-type E3 ubiquitin ligase, is transcriptionally upregulated in HeLa cells expressing Emery-Dreifuss muscular dystrophy-causing-lamin A mutants. However, the role of HECW2 upregulation in mediating downstream effects in lamin mutant-expressing cells was previously unexplored. Here, we show that HECW2 interacts with two lamin A-binding proteins, proliferating cell nuclear antigen (PCNA), via a canonical PCNA-interacting protein (PIP) motif, and lamin B1. HECW2 mediates their ubiquitination and targets them for proteasomal degradation. Cells expressing lamin A mutants G232E and Q294P, in which HECW2 is upregulated, show increased proteasomal degradation of PCNA and lamin B1 most likely mediated by HECW2. Our findings establish HECW2 as an E3 ubiquitin ligase for PCNA and lamin B1 which regulates their levels in laminopathic cells. We also found that HECW2 interacts with wild-type lamin A and ubiquitinates it and this interaction is reduced in case of lamin mutants G232E and Q294P. Our findings suggest that interplay among HECW2, lamin A, PCNA, and lamin B1 determines their respective homeostatic levels in the cell and dysregulation of these interactions may contribute to the pathogenicity of laminopathies. •HECW2 mediates the ubiquitination and proteasomal degradation of PCNA and lamin B1.•HECW2 overexpression stalls cells in S-phase and increases genomic instability.•Lamin A mutants G232E and Q294P upregulate HECW2 in cells.•Lamin A mutants G232E and Q294P promote the degradation of PCNA and lamin B1.•HECW2 mediates the ubiquitination of lamin A but does not degrade it.