In one of the earliest events in human cytomegalovirus (HCMV)-infected cells, the major immediate-early (IE) protein IE1 initially targets to and then disrupts the nuclear structures known as PML oncogenic domains (PODs) or nuclear domain 10. Recent studies have suggested that modification of PML by SUMO is essential to form PODs and that IE1 both binds to PML and may disrupt PODs by preventing or removing SUMO adducts on PML. In this study, we showed that in contrast to herpes simplex virus type 1 (HSV-1) IE110 (ICP0), the loss of sumoylated forms of PML by cotransfected IE1 was resistant to the proteasome inhibitor MG132 and that IE1 did not reduce the level of unmodified PML. Reduced sumoylation of PML was also observed in U373 cells after infection with wild-type HCMV and proved to require IE1 protein expression. Mutational analysis revealed that the central hydrophobic domain of IE1, including Leu174, is required for both PML binding and loss of PML sumoylation and confirmed that all IE1 mutants tested that were deficient in these functions also failed both to target to PODs and to disrupt PODs. These same mutants were also inactive in several reporter gene transactivation assays and in inhibition of PML-mediated repression. Importantly, a viral DNA genome containing an IE1 gene with a deletion [IE1(⌬290-320)] that was defective in these activities was not infectious when transfected into permissive fibroblast cells, but the mutant IE1(K450R), which is defective in IE1 sumoylation, remained infectious. Our mutational analysis strengthens the idea that interference by IE1 with both the sumoylation of PML and its repressor activity requires a physical interaction with PML that also leads to disruption of PODs. These activities of IE1 also correlate with several unusual transcriptional transactivation functions of IE1 and may be requirements for efficient initiation of the lytic cycle in vivo.Human cytomegalovirus (HCMV), a member of the betaherpesvirus subfamily, typically causes nearly ubiquitous asymptomatic latent or persistent infections. However, primary infections of newborns and reactivation from latent infection in immunocompromised individuals, including recipients of organ transplantation and patients with AIDS, can lead to lifethreatening problems with overt systematic and chronic disease (56, 65). During lytic cycle infection, HCMV gene expression occurs in a three-step sequential fashion with immediate-early (IE or ␣), delayed-early (DE or ), and late (L or ␥) kinetics. Among the IE proteins, two nuclear regulatory phosphoproteins, IE1 (or IE72) and IE2 (or IE86), are the first and most abundantly expressed proteins and are synthesized by differential splicing from the same complex overlapping transcription unit within the major IE (MIE) locus (56).The 72-kDa IE1 protein (491 amino acids) is encoded by exons 1, 2, 3, and 4 (UL123), whereas the 86-kDa IE2 protein (579 amino acids) is encoded by exons 1, 2, 3, and 5 (UL122), and the two proteins share 85 amino acids at the N terminus. IE2 is a spe...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.