Document Detail

Ubiquitin-conjugating enzyme 3 delays human lens epithelial cells in metaphase.
MedLine Citation:
PMID:  16565361     Owner:  NLM     Status:  MEDLINE    
PURPOSE: Ubc3/Cdc34 is a ubiquitin-conjugating enzyme (Ubc) with well established functions in the G1-to-S-phase transition. Expecting to find similar effects in human lens epithelial cells (HLECs), the authors explored roles for this ubiquitin-conjugating enzyme in regulation of the HLEC cycle. METHODS: Catalytically incompetent Ubc3 (C88S, L97S), wild-type (wt)Ubc3, and mutant (mt)Ubc2 (C93A) were expressed in HLECs, by using an adenoviral vector, and cell cycle progression was assessed. RESULTS: Expression of mt- and wtUbc3, but not empty virus or mtUbc2, delayed the cell cycle in metaphase, rather than the expected G1 phase. Expression of both Ubc3s also stabilized M-phase regulators, cyclin A, cyclin B, and securin. Thus, it appeared that the Ubc3 enzymes were playing roles different from canonical proteolytic functions in targeting G1/S regulators for degradation. We also directly investigated the effect of inhibiting the proteasome on the cell cycle of HLECs. When the proteasome inhibitor was added to S-phase cells, the M-phase regulators were stabilized, and the cells were arrested in the G2/M phase. In contrast, if the proteasome inhibitor was added before the cells entered the S phase, stabilization of the G1 kinase inhibitors p21WAF and p27KIP was observed and the cells were arrested in the G1 phase. CONCLUSIONS: The ubiquitin-proteasome pathway is involved in regulation of transitions between all phases of the HLEC cycle. However, in contrast with previously described roles for Ubc3 in governing G1/S transitions, expression of Ubc3 delays the HLEC cycle in metaphase. The data suggest novel roles for Ubc3 that do not involve the transfer of ubiquitin in the M phase in the HLEC cell cycle.
Qing Liu; Fu Shang; Elizabeth Whitcomb; Weimin Guo; Wei Li; Allen Taylor
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  47     ISSN:  0146-0404     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2006 Apr 
Date Detail:
Created Date:  2006-03-27     Completed Date:  2006-04-27     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1302-9     Citation Subset:  IM    
Laboratory for Nutrition and Vision Research, JMUSDA-HNRCA at Tufts University, Boston, Massachusetts 02111, USA.
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MeSH Terms
Adenoviridae / genetics
Blotting, Western
Cell Culture Techniques
Cyclin-Dependent Kinase Inhibitor p21 / metabolism
Cyclin-Dependent Kinase Inhibitor p27 / metabolism
Epithelial Cells / cytology
Flow Cytometry
Gene Expression Regulation, Enzymologic / physiology
Genetic Vectors
Lens, Crystalline / cytology*
Metaphase / physiology*
Microscopy, Fluorescence
Microtubules / metabolism
Nocodazole / pharmacology
Ubiquitin-Protein Ligase Complexes / physiology*
Grant Support
Reg. No./Substance:
0/Cdkn1a protein, mouse; 0/Cyclin-Dependent Kinase Inhibitor p21; 147604-94-2/Cyclin-Dependent Kinase Inhibitor p27; 31430-18-9/Nocodazole; EC Ligase Complexes; EC complex

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