6tgz | pdb_00006tgz
IE1 from human cytomegalovirus
Structural highlights
FunctionVIE1_HCMVA Plays an important role in transactivating viral early genes as well as activating its own promoter, probably by altering the viral chromatin structure (By similarity). Expression of IE1 and IE2 proteins is critical for the establishment of lytic infection and reactivation from viral latency (PubMed:27466417). Disrupts PML-associated ND10 nuclear bodies by interfering with host PML and SP100 sumoylation thereby altering the regulation of type I and type II interferon-induced gene expression (Probable) (PubMed:27903803). Promotes efficient viral growth by interacting with and directing host SP100 to degradation, leading to enhanced acetylation level of histones (By similarity). In addition, functions in counteracting the host innate antiviral response. Inhibits the type I interferon pathway by directly interacting with and sequestrating host STAT2 (By similarity). Also targets type II interferon pathway by repressing IL6- and STAT3 target genes (By similarity). Repression of STAT3 genes is due to STAT3 nuclear accumulation and disruption of IL6-induced STAT3 phosphorylation by IE1 (PubMed:23903834). This repression is followed by phosphorylation and activation of STAT1 (By similarity). Inhibits host ISG transcription by sequestering host ISGF3 in a PML- and STAT2- binding dependent manner (By similarity). Alters host cell cycle progression, probably through its interaction with host E2F1 or RB1 that overcomes the RB1-mediated repression of E2F-responsive promoters (By similarity).[UniProtKB:P03169][1] [2] [3] [4] Publication Abstract from PubMedRestriction factors are potent antiviral proteins that constitute a first line of intracellular defense by blocking viral replication and spread. During co-evolution, however, viruses have developed antagonistic proteins to modulate or degrade the restriction factors of their host. To ensure the success of lytic replication, the herpesvirus human cytomegalovirus (HCMV) expresses the immediate-early protein IE1, which acts as an antagonist of antiviral, subnuclear structures termed PML nuclear bodies (PML-NBs). IE1 interacts directly with PML, the key protein of PML-NBs, through its core domain and disrupts the dot-like multiprotein complexes thereby abrogating the antiviral effects. Here we present the crystal structures of the human and rat cytomegalovirus core domain (IE1CORE). We found that IE1CORE domains, also including the previously characterized IE1CORE of rhesus CMV, form a distinct class of proteins that are characterized by a highly similar and unique tertiary fold and quaternary assembly. This contrasts to a marked amino acid sequence diversity suggesting that strong positive selection evolved a conserved fold, while immune selection pressure may have fostered sequence divergence of IE1. At the same time, we detected specific differences in the helix arrangements of primate versus rodent IE1CORE structures. Functional characterization revealed a conserved mechanism of PML-NB disruption, however, primate and rodent IE1 proteins were only effective in cells of the natural host species but not during cross-species infection. Remarkably, we observed that expression of HCMV IE1 allows rat cytomegalovirus replication in human cells. We conclude that cytomegaloviruses have evolved a distinct protein tertiary structure of IE1 to effectively bind and inactivate an important cellular restriction factor. Furthermore, our data show that the IE1 fold has been adapted to maximize the efficacy of PML targeting in a species-specific manner and support the concept that the PML-NBs-based intrinsic defense constitutes a barrier to cross-species transmission of HCMV. Cytomegalovirus immediate-early 1 proteins form a structurally distinct protein class with adaptations determining cross-species barriers.,Schweininger J, Scherer M, Rothemund F, Schilling EM, Worz S, Stamminger T, Muller YA PLoS Pathog. 2021 Aug 9;17(8):e1009863. doi: 10.1371/journal.ppat.1009863., eCollection 2021 Aug. PMID:34370791[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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