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Published on: May 10, 2022
hMMS2 serves a redundant role in human PCNA polyubiquitination
Jan Brun1, Roland Chiu, Katherine Lockhart
1Centre for Cancer Therapeutics, Ottawa Health Research Institute, Ottawa, ON K1H 8L6, Canada. jzbrun@yahoo.com
BMC Molecular Biology
|February 21, 2008
Summary
Human cells maintain PCNA polyubiquitination even when MMS2 is reduced, suggesting redundancy in the DNA damage tolerance pathway. This indicates a potential compensatory mechanism for MMS2 loss in DNA repair.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- DNA damage triggers PCNA ubiquitination in yeast, directing DNA damage tolerance (DDT) pathways.
- PCNA monoubiquitination by RAD18/RAD6 leads to error-prone bypass.
- PCNA polyubiquitination by RAD5/UBC13/MMS2 governs error-free repair via K63-polyUb chains.
Purpose of the Study:
- Investigate the role of human MMS2 (hMMS2) in PCNA polyubiquitination.
- Determine if hMMS2 is essential for PCNA polyubiquitination in mammalian cells.
- Explore redundancy within the DNA damage tolerance pathway.
Main Methods:
- siRNA-mediated knockdown of MMS2, RAD18, and UBC13 in mammalian cells.
- Analysis of PCNA ubiquitination status following knockdown.
- Assessment of PCNA polyubiquitination in MMS2-deficient mouse embryonic stem cells, with and without UEV1A depletion.
Main Results:
- Mammalian cells with reduced MMS2 maintain PCNA polyubiquitination.
- Knockdown of RAD18 or UBC13 abrogates PCNA ubiquitination.
- Depletion of UEV1A (MMS2 homolog) does not affect PCNA polyubiquitination.
- MMS2-null mouse embryonic stem cells exhibit normal PCNA polyubiquitination kinetics.
Conclusions:
- The DNA damage tolerance pathway exhibits significant redundancy.
- A compensatory mechanism, possibly involving another hMMS2 variant or complex, exists for the loss of hMMS2.
- PCNA polyubiquitination is robust and can be maintained despite the absence of key components like hMMS2.
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