Structural and Functional Characterization of Herpes Simplex Virus 1 Immediate-Early Protein Infected-Cell Protein 22

Wei, Cun; Liu, Long-ding; Dong, Chuanfu; Luo, Jie; Li, Qihan

doi:10.1093/jb/mvj135

Cited by 14 publications

(22 citation statements)

References 25 publications

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“…1C, panel a) localized diffusely in the nucleus and to discrete nuclear bodies. This pattern is similar to that which has been reported by others for transiently expressed ICP22 (7,48,54). In contrast, the US1.5 form of the protein (Fig.…”

Section: Resultssupporting

confidence: 91%

“…The nature of the ICP22-containing nuclear bodies is currently unknown, although their presence in transfected cells indicates that they are either preexisting cellular structures or are induced de novo by ICP22. Recent work indicates that they do not correspond to PML domains, Cajal bodies, or SC35-containing nuclear speckles (7,48), although they appear to have a paired spatial relationship with SC35 speckles (7,48). Whatever their physical nature, our results demonstrate two important points concerning their relationship to ICP22.…”

Section: Discussionmentioning

confidence: 47%

“…Additionally, all of the proteins are expressed at roughly comparable levels in Vero cells. ICP22 is reported to localize to the nucleus in both infected and transfected cells (7,22,48,54). We used immunofluorescence to see whether the mutant proteins were similarly localized.…”

Section: Resultsmentioning

confidence: 99%

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Identification of Sequences in Herpes Simplex Virus Type 1 ICP22 That Influence RNA Polymerase II Modification and Viral Late Gene Expression

Bastian

Rice

2009

J Virol

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Previous studies have shown that the herpes simplex virus type 1 (HSV-1) immediate-early protein ICP22 alters the phosphorylation of the host cell RNA polymerase II (Pol II) during viral infection. In this study, we have engineered several ICP22 plasmid and virus mutants in order to map the ICP22 sequences that are involved in this function. We identify a region in the C-terminal half of ICP22 (residues 240 to 340) that is critical for Pol II modification and further show that the N-terminal half of the protein (residues 1 to 239) is not required. However, immunofluorescence analysis indicates that the N-terminal half of ICP22 is needed for its localization to nuclear body structures. These results demonstrate that ICP22's effects on Pol II do not require that it accumulate in nuclear bodies. As ICP22 is known to enhance viral late gene expression during infection of certain cultured cells, including human embryonic lung (HEL) cells, we used our engineered viral mutants to map this function of ICP22. It was found that mutations in both the N-and C-terminal halves of ICP22 result in similar defects in viral late gene expression and growth in HEL cells, despite having distinctly different effects on Pol II. Thus, our results genetically uncouple ICP22's effects on Pol II from its effects on viral late gene expression. This suggests that these two functions of ICP22 may be due to distinct activities of the protein.Herpes simplex virus type 1 (HSV-1) is a widely studied human alphaherpesvirus that serves as an important model for defining the fundamental pathways used by herpesviruses to replicate in their host cells. During productive infection, the 152-kb double-stranded HSV-1 genome is rapidly translocated to the nucleus where the ϳ80 viral genes are transcribed by the host cell RNA polymerase II (Pol II) in a temporally orchestrated program that is regulated by viral proteins (reviewed in reference 47). The first genes to be expressed are the immediate-early (IE) genes. Transcription of these genes requires the viral tegument protein VP16 but does not require new viral protein synthesis. Translation of the IE genes results in expression of five proteins, four of which (ICP0, ICP4, ICP22, and ICP27) serve to activate and temporally regulate the ensuing expression of the delayed-early (DE) and late (L) genes.At the same time that HSV-1 DE and L genes are induced to high levels, host cell gene expression is largely inhibited, a phenomenon known as host shutoff. Host shutoff is a complex process that is mediated at multiple levels of gene expression and is regulated by several viral factors (reviewed in reference 52). A number of studies have investigated whether HSV-1-mediated shutoff involves the inhibition of Pol II transcription on host cell genes (20,24,37,51,53,55). Such studies have used either nuclear run-on transcription analysis or metabolic pulse-labeling of RNA to directly measure the transcription rates of specific host genes following infection or, in some cases, of adenoviral or polyomaviral genes tha...

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Section: Resultssupporting

confidence: 91%

Section: Discussionmentioning

confidence: 47%

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Identification of Sequences in Herpes Simplex Virus Type 1 ICP22 That Influence RNA Polymerase II Modification and Viral Late Gene Expression

Bastian

Rice

2009

J Virol

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“…This study further demonstrated that the repressive function of ICP22 was partially abrogated by coexpression of the U L 13 gene, which encodes a viral Ser/Thr kinase. The observed repression of viral gene expression by ICP22 first noted by Prod'hon et al has been corroborated by several groups (2,5). To date, however, the mechanism underlying this repression remains unclear.…”

Section: Replication Of Icp22mentioning

confidence: 66%

“…Using the pCDNA3:ICP22 expression cassette, Fraser and Rice demonstrated that ICP22 alone is sufficient to alter the phosphorylation state of the C-terminal domain of RNA Pol II. A similar strategy using the pCDNA3 vector was employed by Cun et al to demonstrate transcriptional repression by ICP22 alone (2). The use of the CMV promoter in pCDNA3 as an engine to drive ICP22 expression presents numerous opportunities for screening and characterizing mutant forms of ICP22 without the need to introduce mutations directly into the viral genome.…”

Section: Replication Of Icp22mentioning

confidence: 99%

Transient Expression of Herpes Simplex Virus Type 1 ICP22 Represses Viral Promoter Activity and Complements the Replication of an ICP22 Null Virus

Bowman

Orlando

Davido

et al. 2009

J Virol

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Of the five herpes simplex virus type 1 immediate early (IE) proteins, the least is known about the function of ICP22 during productive infection and latency. Research characterizing the physical and functional properties of the protein has been limited because ICP22 has proven to be difficult to express in transient assays. In addition, genetic analysis of ICP22 has been complicated by the fact that the C terminus of ICP22 is expressed as a discrete protein product. In order to characterize properties of mutant and wild-type ICP22, we developed a transient expression system. We found that ICP22 can be expressed at detectable levels when placed under the control of the cytomegalovirus IE promoter, confirming recent observations by K. A. Fraser and S. A. Rice (J. Virol. 81:5091-5101, 2007). We extended this analysis to show that ICP22 can also be expressed from its own promoter in the presence of other viral factors, either by coexpression with ICP0 or by infection with an ICP22 null virus. Notably, infection of cells transfected with an ICP22 expression vector yielded ICP22 protein that was modified in a manner similar to that of ICP22 protein detected in wild-typeinfected cells. We go on to demonstrate that the failure of ICP22 protein to be expressed in transiently transfected cells was not due to inactivity of the ICP22 promoter, but rather to the ability of ICP22 to inhibit expression of reporter gene activity, including its own, in transient assays. Of special note was the observation that expression of ICP22 was sufficient to prevent transactivation of reporter genes by ICP0. Finally, transient expression of ICP22 was sufficient to complement replication of an ICP22 null virus, demonstrating that this system can be used to study functional properties of ICP22. Collectively, this transient expression system facilitates tests of the physical and functional properties of ICP22 and ICP22 mutants prior to introduction of mutant genes into the viral genome.

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Characterization of the subcellular localization of herpes simplex virus type 1 proteins in living cells

Xing

Wang

You

et al. 2010

Med Microbiol Immunol

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In this study, we presented the construction of a library of expression clones for the herpes simplex virus type 1 (HSV-1) proteome and subcellular localization map of HSV-1 proteins in living cells using yellow fluorescent protein (YFP) fusion proteins. As a result, 21 proteins showed cytoplasmic or subcytoplasmic localization, 16 proteins showed nuclear or subnuclear localization, and others were present both in the nucleus and cytoplasm. Interestingly, most capsid proteins showed enriched or exclusive localization in the nucleus, and most of the envelope proteins showed cytoplasmic localization, suggesting that subcellular localization of the proteins correlated with their functions during virus replication. These results present a subcellular localization map of HSV-1 proteins in living cells, which provide useful information to further characterize the functions of these proteins.

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Structural and Functional Characterization of Herpes Simplex Virus 1 Immediate-Early Protein Infected-Cell Protein 22

Cited by 14 publications

References 25 publications

Identification of Sequences in Herpes Simplex Virus Type 1 ICP22 That Influence RNA Polymerase II Modification and Viral Late Gene Expression

Identification of Sequences in Herpes Simplex Virus Type 1 ICP22 That Influence RNA Polymerase II Modification and Viral Late Gene Expression

Transient Expression of Herpes Simplex Virus Type 1 ICP22 Represses Viral Promoter Activity and Complements the Replication of an ICP22 Null Virus

Characterization of the subcellular localization of herpes simplex virus type 1 proteins in living cells

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