SUMOylation of the human cytomegalovirus 72-kilodalton IE1 protein facilitates expression of the 86-kilodalton IE2 protein and promotes viral replication.
The 72-kDa immediate-early 1 protein (IE1-72kDa) of human cytomegalovirus has been previously shown to be posttranslationally modified by covalent conjugation to the ubiquitin-related protein SUMO-1. Using an infectious bacterial artificial chromosome clone of human cytomegalovirus, we constructed a mutant virus (BADpmIE1-K450R) that is deficient for SUMOylation of IE1-72 kDa due to a single amino acid exchange in the SUMO-1 attachment site. Compared to wild-type virus, this mutant grew more slowly and generated a reduced yield in infected human fibroblasts, indicating that SUMO modification is required for the full activity of IE1-72 kDa. The lack of SUMOylation did not affect the intranuclear localization of IE1-72 kDa, including its ability to target to and disrupt PML bodies and to bind to mitotic chromatin. Likewise, SUMOylation-deficient IE1-72 kDa activated several viral promoters as efficiently as the wild-type protein. However, the failure to modify IE1-72 kDa resulted in substantially reduced levels of the IE2 transcript and its 86-kDa protein (IE2-86 kDa). These observations suggest that SUMO modification of IE1-72 kDa contributes to efficient HCMV replication by promoting the accumulation of IE2-86 kDa.
Nevels
Michael
M
Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, USA.
Brune
Wolfram
W
Shenk
Thomas
T
D002460:Cell Line; D022202:Chromosomes, Artificial, Bacterial; D003587:Cytomegalovirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity / Q000502:physiology*; D015967:Gene Expression Regulation, Viral; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D025842:SUMO-1 Protein / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
C088645:IE1 protein, cytomegalovirus; C069186:IE2 protein, Cytomegalovirus; D017874:Immediate-Early Proteins; D025842:SUMO-1 Protein; D015534:Trans-Activators; D014764:Viral Proteins