Orc2 protects ORCA from ubiquitin-mediated degradation

Research output: Contribution to journalArticle

Abstract

Origin recognition complex (ORC) is highly dynamic, with several ORC subunits getting posttranslationally modified by phosphorylation or ubiquitination in a cell cycle-dependent manner. We have previously demonstrated that a WD repeat containing protein ORC-associated (ORCA/LRWD1) stabilizes the ORC on chromatin and facilitates pre-RC assembly. Further, ORCA levels are cell cycle-regulated, with highest levels during G1, and progressively decreasing during S phase, but the mechanism remains to be elucidated. We now demonstrate that ORCA is polyubiquitinated in vivo, with elevated ubiquitination observed at the G1/S boundary. ORCA utilizes lysine-48 (K48) ubiquitin linkage, suggesting that ORCA ubiquitination mediates its regulated degradation. Ubiquitinated ORCA is re-localized in the form of nuclear aggregates and is predominantly associated with chromatin. We demonstrate that ORCA associates with the E3 ubiquitin ligase Cul4A-Ddb1. ORCA is ubiquitinated at the WD40 repeat domain, a region that is also recognized by Orc2. Furthermore, Orc2 associates only with the non-ubiquitinated form of ORCA, and Orc2 depletion results in the proteasome-mediated destabilization of ORCA. Based on the results, we suggest that Orc2 protects ORCA from ubiquitin-mediated degradation in vivo.

Original languageEnglish (US)
Pages (from-to)3578-3589
Number of pages12
JournalCell Cycle
Volume11
Issue number19
DOIs
StatePublished - Oct 1 2012

Fingerprint

Origin Recognition Complex
Ubiquitin
Ubiquitination
Chromatin
Cell Cycle
Ubiquitin-Protein Ligases
Proteasome Endopeptidase Complex
S Phase
Lysine
Phosphorylation

Keywords

  • Cul4A-Ddb1
  • ORC
  • ORCA/LRWD1
  • Pre-RC
  • Replication
  • Ubiquitination

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

Cite this

Orc2 protects ORCA from ubiquitin-mediated degradation. / Shen, Zhen; Prasanth, Supriya G.

In: Cell Cycle, Vol. 11, No. 19, 01.10.2012, p. 3578-3589.

Research output: Contribution to journalArticle

Shen, Zhen ; Prasanth, Supriya G. / Orc2 protects ORCA from ubiquitin-mediated degradation. In: Cell Cycle. 2012 ; Vol. 11, No. 19. pp. 3578-3589.
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