Herpes simplex virus type 1 tegument protein VP22 interacts with TAF-I proteins and inhibits nucleosome assembly but not regulation of histone acetylation by INHAT

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253

During infection by herpes simplex virus type 1 (HSV-1), the virion protein VP16 activates the transcription of viral immediate-early (IE) genes. Genetic and biochemical assays have shown that the potent transcriptional activation domain of VP16 can associate with general transcription factors and with chromatin-modifying coactivator proteins of several types. The latter interactions are particularly intriguing because previous reports indicate that HSV-1 DNA does not become nucleosomal during lytic infection. In the present work, chemical cross-linking and immunoprecipitation assays were used to probe the presence of activators, general transcription factors, and chromatin-modifying coactivators at IE gene promoters during infection of HeLa cells by wild-type HSV-1 and by RP5, a viral strain lacking the VP16 transcriptional activation domain. The presence of VP16 and Oct-1 at IE promoters did not depend on the activation domain. In contrast, association of RNA polymerase II, TATA-binding protein, histone acetyltransferases (p300 and CBP), and ATP-dependent remodeling proteins (BRG1 and hBRM) with IE gene promoters was observed in wild-type infections but was absent or reduced in cells infected by RP5. In contrast to the previous evidence for nonnucleosomal HSV-1 DNA, histone H3 was found associated with viral DNA at early times of infection. Interestingly, histone H3 was underrepresented on IE promoters in a manner dependent on the VP16 activation domain. Thus, the VP16 activation domain is responsible for recruiting general transcription factors and coactivators to IE promoters and also for dramatically reducing the association of histones with those promoters.The activation domain of VP16 (VP16 AD) from herpes simplex virus type I (HSV-1) has been widely used as a model for the study of transcriptional activation in eukaryotes. During infection, VP16 triggers the cascade of viral gene expression by activating transcription of the viral immediate-early (IE) genes (65). VP16 forms a DNA-binding complex with the cellular proteins Oct-1 and HCF-1 at specific cis elements present in the IE gene promoters (27,40,48,68). The potent VP16 AD (10, 55), often artificially fused to a heterologous DNA-binding domain (47), can activate transcription in a wide range of organisms, including yeasts, insects, plants, and mammals (3,47,58,66), indicating that mechanisms of transcriptional activation are broadly conserved through evolution.Interactions of the VP16 AD with general transcription factors (GTFs) including transcription factor IIB (TFIIB), TFIIH, TATA-binding protein (TBP), and TBP-associated factors (TAFs) suggest that the VP16 AD might activate transcription by stimulating the assembly of an RNA polymerase II (RNA Pol II) preinitiation complex (13,17,24,31,56,67). Consistent with this model, in vitro experiments have demonstrated the ability of the VP16 AD to promote the formation of the ternary complex formed by TFIIA, TFIID, and TATA box DNA (25). The VP16 AD might also recruit the RNA Pol II holoenzyme through i...

Section: Discussionmentioning

confidence: 67%

VP16-Dependent Association of Chromatin-Modifying Coactivators and Underrepresentation of Histones at Immediate-Early Gene Promoters during Herpes Simplex Virus Infection

Herrera

Triezenberg

2004

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253

“…The finding that the VP22LL251AA mutation, which impaired viral replication and neurovirulence in mice, also attenuated the ability of VP22 to promote the cytoplasmic localization and expression of a number of viral and cellular proteins suggested that these VP22 functions may be critical for viral replication and neurovirulence in vivo. However, the VP22LL251AA mutation may affect a VP22 function(s) other than those identified in this study, since we have not investigated whether Di-Leu-251-252 is required for other VP22 functions, such as functional interaction with microtubules, chromatin, RNA, and cellular membranes (4,17,18,34,43,54,59,66). Further studies to identify other VP22 functions that require Di-Leu-251-252 are needed and are under way in our laboratories.…”

Section: Discussionmentioning

confidence: 99%

“…Although the precise mechanism(s) by which VP22 acts in viral replication and pathogenesis remains largely unknown at present, a number of functions for VP22 have been reported. These include (i) association with and reorganization of microtubules (18,34); (ii) interaction with chromatin, histones H1 and H4, and template-activating factor 1 (TAF-1), a chromatin-remodeling factor, and impairment of histone acetylation and TAF-1-dependent nucleosome assembly (17,43,54,66); (iii) neutralization of the activity of VHS (62); (iv) binding to a viral RNA and transport of the RNA from cell to cell for expression (59); (v) association with cellular membranes and localization in acidic compartments, including the trans-Golgi network, where HSV-1 nucleocapsids may acquire their final envelope (4,61); (vi) interaction with various viral tegument and envelope proteins, including VP16, ICP0, Us9, UL46, UL47, UL56, glycoprotein E (gE), gD, and gM (7,16,21,22,24,25,35,42,50); (vii) promotion of the synthesis of various viral proteins in infected cells and incorporation of a subset of virion-assembled proteins (13)(14)(15); and (viii) regulation of the compartmentalization of VP16 and ICP0 (15,16). Although many VP22 functions have been clarified, as described above, and the domains responsible for some VP22 functions have been mapped, none of these functions have been explicitly linked to HSV-1 replication and pathogenesis.…”

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confidence: 99%

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confidence: 99%

See 1 more Smart Citation

Herpes Simplex Virus 1 VP22 Regulates Translocation of Multiple Viral and Cellular Proteins and Promotes Neurovirulence

Tanaka

Kato

Satoh

et al. 2012

Herpes simplex virus 1 (HSV-1) protein VP22, encoded by the UL49 gene, is a major virion tegument protein. In the present study, we showed that VP22 was required for efficient redistribution of viral proteins VP16, VP26, ICP0, ICP4, and ICP27 and of cellular protein Hsc-70 to the cytoplasm of infected cells. We found that two dileucine motifs in VP22, at amino acids 235 and 236 and amino acids 251 and 252, were necessary for VP22 regulation of the proper cytoplasmic localization of these viral and cellular proteins. The dileucine motifs were also required for proper cytoplasmic localization of VP22 itself and for optimal expression of viral proteins VP16, VP22, ICP0, UL41, and glycoprotein B. Interestingly, a recombinant mutant virus with alanines substituted for the dileucines at amino acids 251 and 252 had a 50% lethal dose (LD 50 ) for neurovirulence in mice following intracerebral inoculation about 10 3 -fold lower than the LD 50 of the repaired virus. Furthermore, the replication and spread of this mutant virus in the brains of mice following intracerebral inoculation were significantly impaired relative to those of the repaired virus. The ability of VP22 to regulate the localization and expression of various viral and cellular proteins, as shown in this study, was correlated with an increase in viral replication and neurovirulence in the experimental murine model. Thus, HSV-1 VP22 is a significant neurovirulence factor in vivo. Herpes simplex virus 1 (HSV-1) virions, like those of other herpesviruses, consist of three morphologically distinct structures: the nucleocapsid, containing the linear doublestranded DNA viral genome, which encodes at least 84 viral proteins, in an icosahedral capsid; the tegument, a proteinaceous layer surrounding the nucleocapsid; and the envelope, a host cellderived lipid bilayer with viral glycoproteins enclosing the nucleocapsid and tegument (55). The tegument consists of a large number of proteins, including at least 26 viral proteins (41). Tegument proteins are released into the cytoplasm upon the fusion of the virion envelope with the host cell membrane and therefore may function to establish an environment for effective initiation of very early infection. However, the roles of only a few tegument proteins, including the immediate-early gene transactivator VP16, encoded by the UL48 gene, and the virion host shutoff protein VHS, encoded by the UL41 gene (55), in very early infection have been established. Large amounts of newly synthesized tegument proteins have also been shown to modulate the host cellular environment and to regulate various viral replication processes later in infection (28).VP22, encoded by the UL49 gene, is one of the major HSV-1 tegument proteins, and its amino acid sequence is conserved in the subfamily Alphaherpesvirinae. It appears that the functional requirements of VP22 homologues in the viral life cycle differ among alphaherpesviruses. For example, the VP22 homologues of Marek's disease virus serotype 1 and varicella-zoster virus are considered to...

“…For example, there is a growing body of evidence that HSV-1 replication is regulated in part by nucleosome-based mechanisms (reviewed in reference 23). VP22 may promote transcription at late times in infection, when it is present in infected cells in large amounts, via its interactions with the linker histone H1, the core histone H4, or the H2A-H2B-specific histone chaperone template-activating factor I (32,43). Alternatively, VP22 may increase mRNA abundance by protecting it from degradation through its RNA-binding activity (34).…”

Section: Discussionmentioning

confidence: 99%

Deletion of the Herpes Simplex Virus 1 U _L 49 Gene Results in mRNA and Protein Translation Defects That Are Complemented by Secondary Mutations in U _L 41

Mbong

Woodley

Dunkerley

et al. 2012

؊ protein synthesis defect, and the rescue by secondary mutations in vhs, occurred at the mRNA and/or translational levels, quantitative reverse transcriptase PCR (qRT-PCR) and polysome analyses were performed. We found that the absence of VP22 caused a small decrease in mRNA levels as well as a defect in polysome assembly that was independent of mRNA abundance. Both defects were complemented by the secondary mutations in vhs, indicating functional interplay between VP22 and vhs in both accumulation and translation of viral mRNAs.