Proteasome-dependent disruption of the E3 ubiquitin ligase anaphase-promoting complex by HCMV protein pUL21a.
The anaphase-promoting complex (APC) is an E3 ubiquitin ligase which controls ubiquitination and degradation of multiple cell cycle regulatory proteins. During infection, human cytomegalovirus (HCMV), a widespread pathogen, not only phosphorylates the APC coactivator Cdh1 via the multifunctional viral kinase pUL97, it also promotes degradation of APC subunits via an unknown mechanism. Using a proteomics approach, we found that a recently identified HCMV protein, pUL21a, interacted with the APC. Importantly, we determined that expression of pUL21a was necessary and sufficient for proteasome-dependent degradation of APC subunits APC4 and APC5. This resulted in APC disruption and required pUL21a binding to the APC. We have identified the proline-arginine amino acid pair at residues 109-110 in pUL21a to be critical for its ability to bind and regulate the APC. A point mutant virus in which proline-arginine were mutated to alanines (PR-AA) grew at wild-type levels. However, a double mutant virus in which the viral ability to regulate the APC was abrogated by both PR-AA point mutation and UL97 deletion was markedly more attenuated compared to the UL97 deletion virus alone. This suggests that these mutations are synthetically lethal, and that HCMV exploits two viral factors to ensure successful disruption of the APC to overcome its restriction on virus infection. This study reveals the HCMV protein pUL21a as a novel APC regulator and uncovers a unique viral mechanism to subvert APC activity.
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Anthony R
AR
Fehr
Nathaniel C
NC
Gualberto
John Paul
JP
Savaryn
Scott S
SS
Terhune
Dong
D
Yu
D064173:Anaphase-Promoting Complex-Cyclosome; D064192:Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome; D064193:Apc5 Subunit, Anaphase-Promoting Complex-Cyclosome; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D003587:Cytomegalovirus / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D017384:Sequence Deletion; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
C577369:ANAPC4 protein, human; C577375:ANAPC5 protein, human; D064192:Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome; D064193:Apc5 Subunit, Anaphase-Promoting Complex-Cyclosome; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D014764:Viral Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex