Immediate early protein IE63 of herpes simplex virus type 1 binds RNA directly

The herpes simplex virus (HSV) ICP27 immediate-early protein plays an essential role in the expression of viral late genes. ICP27 is a multifunctional protein and has been reported to regulate multiple steps of mRNA synthesis and processing, including transcription, splicing, and nuclear export. Recently, ICP27 was reported to interact with translation factors and to stimulate translation of the viral late mRNA encoding VP16. We examined the effects of ICP27 on accumulation, nuclear export, and translation of HSV 1 (HSV-1) late mRNAs encoding VP16, ICP5, and gD. We confirm here that ICP27 stimulates translation of VP16 mRNA as well as an additional HSV-1 late ICP5 mRNA. The data presented here demonstrate that translation levels of both VP16 and ICP5 mRNA is reduced during infections with the ICP27-null virus mutant d27-1, and with ICP27 C-terminal deletion mutant viruses n406 and n504, compared to wild-type virus. In contrast, the translation of gD mRNA is not affected by the presence of ICP27 during infection. These data demonstrate that ICP27 functions to increase the translation levels of a subset of HSV-1 late genes, and this function requires the C terminus of ICP27.

Section: Discussionmentioning

confidence: 99%

Herpes Simplex Virus ICP27 Increases Translation of a Subset of Viral Late mRNAs

Fontaine-Rodriguez

Knipe

2008

“…ICP8, the major DNA-binding protein encoded by HSV, interacts with DNA both in vitro and in vivo (46). Likewise, ICP27 is known to interact with RNA in vitro (7,38,53,76). The RNA-binding properties of ICP27 and the DNA-binding property of ICP8 raised the possibility that their associations with Pol II might be mediated by RNA or DNA.…”

Section: Coprecipitation Of Hsv Proteins With An Anti-srb7 Antibodymentioning

confidence: 99%

“…ICP27 promotes transcription of at least some late genes, e.g., the gC and U L 47 genes, in infected Vero cells (39). Evidence for posttranscriptional effects of ICP27 include the observations that ICP27 binds RNA via its RGG motif (7,38,53,76), regulates pre-mRNA 3Ј processing (33,51,52), stabilizes labile 3Ј ends of mRNA (7), interacts with cellular protein p32 (8) and spliceosome-associated protein 145 (9), inhibits the splicing of both viral and cellular transcripts (34), induces retention of intron-containing transcripts in the nucleus (61) but shuttles viral intronless transcripts from the nucleus to the cytoplasm (60,76,83), and regulates distribution of host small nuclear ribonucleoproteins (snRNPs) (59,78). In addition, ICP27 has been found to interact with ICP0 and ICP4 (54,57), to colocalize with ICP4 within HSV replication compartments in infected cells (23) and transfected cells (102), and to affect the posttranslational modification and DNA-binding ability of ICP4 (57,97,98).…”

mentioning

confidence: 99%

Association of Herpes Simplex Virus Type 1 ICP8 and ICP27 Proteins with Cellular RNA Polymerase II Holoenzyme

Zhou

Knipe

2002

Herpes simplex virus 1 (HSV-1) infection causes the shutoff of host gene transcription and the induction of a transcriptional program of viral gene expression. Cellular RNA polymerase II is responsible for transcription of all the viral genes, but several viral proteins stimulate viral gene transcription. ICP4 is required for all delayed-early and late gene transcription, ICP0 stimulates transcription of viral genes, and ICP27 stimulates expression of some early genes and transcription of at least some late viral genes. The early DNA-binding protein, ICP8, also stimulates late gene transcription. We therefore investigated which HSV proteins interact with RNA polymerase II. Using immunoprecipitation and Western blotting methods, we observed the coprecipitation of ICP27 and ICP8 with RNA polymerase II holoenzyme. The association of ICP27 with RNA polymerase II was detectable as early as 3 h postinfection, while ICP8 association became evident by 5 h postinfection, and the association of both was independent of viral DNA synthesis. Infections with ICP27 gene mutant viruses revealed that ICP27 is required for the association of ICP8 with RNA polymerase II, while studies with ICP8 gene deletion mutants showed no apparent role for ICP8 in the association of ICP27 with RNA polymerase II. The association of ICP27 and ICP8 with RNA polymerase II holoenzyme appeared to be independent of nucleic acids. We hypothesize that the interaction of ICP27 with RNA polymerase II holoenzyme reflects its role in stimulating early and late gene expression and/or its role in inhibiting host transcription and that the interaction of ICP8 with RNA polymerase II holoenzyme reflects its role in stimulating late gene transcription

“…ICP27 also impairs pre-mRNA splicing via multiple contacts with the splicing machinery (1,19,20, 36, 55,70,71). More recently, intensive studies have shown that ICP27 enhances the efficiency of nuclear export of intronless HSV-1 mRNAs (3,4,30,69,79).ICP27 is an RNA binding protein that shuttles between the nucleus and the cytoplasm (23, 47, 48,56,69,79). It contains an arginine-rich RGG box that is required for RNA binding (48,69), as well as two nuclear localization sequences (46) and a leucine-rich sequence that bears a strong resemblance to the nuclear export sequence (NES) of the human immunodeficiency virus (HIV) protein Rev (69).…”

mentioning

confidence: 99%

“…ICP27 is an RNA binding protein that shuttles between the nucleus and the cytoplasm (23, 47, 48,56,69,79). It contains an arginine-rich RGG box that is required for RNA binding (48,69), as well as two nuclear localization sequences (46) and a leucine-rich sequence that bears a strong resemblance to the nuclear export sequence (NES) of the human immunodeficiency virus (HIV) protein Rev (69).…”

mentioning

confidence: 99%

Control of VP16 Translation by the Herpes Simplex Virus Type 1 Immediate-Early Protein ICP27

Ellison

Maranchuk

Mottet

et al. 2005

Herpes simplex virus (HSV) ICP27 is an essential and multifunctional regulator of gene expression that modulates the synthesis and maturation of viral and cellular mRNAs. Processes that are affected by ICP27 include transcription, pre-mRNA splicing, polyadenylation, and nuclear RNA export. We have examined how ICP27 influences the expression of the essential HSV tegument protein and transactivator of immediate-early gene expression VP16. We monitored the effects of ICP27 on the levels, nuclear export, and polyribosomal association of VP16 mRNA and on the amount and stability of VP16 protein. Deletion of ICP27 reduced the levels of VP16 mRNA without altering its nuclear export or the stability of the encoded protein. However, the translational yield of the VP16 mRNA produced in the absence of ICP27 was reduced 9-to 80-fold relative to that for wild-type infection, suggesting a defect in translation. In the absence of ICP27, the majority of cytoplasmic VP16 mRNA was not associated with actively translating polyribosomes but instead cosedimented with 40S ribosomal subunits, indicating that the translational defect is likely at the level of initiation. These effects were mRNA specific, as polyribosomal analysis of two cellular transcripts (glyceraldehyde-3-phosphate dehydrogenase and ␤-actin) and two early HSV transcripts (thymidine kinase and ICP8) indicated that ICP27 is not required for efficient translation of these mRNAs. Thus, we have uncovered a novel mRNA-specific translational regulatory function of ICP27.Lytic infection by herpes simplex virus type 1 (HSV-1) is characterized by shutoff of host protein synthesis and the temporally regulated expression of three classes of viral genes: immediate-early (IE), early (E), and late (L) (reviewed in reference 66). The infectious cycle is initiated by the virion transactivator VP16, which upon delivery into host cells acts in concert with cellular factors to induce the expression of the five IE genes. Four of these encode nuclear regulatory proteins (ICP0, ICP22, ICP4, and ICP27) that orchestrate the timely expression of the E and L genes. ICP27 plays an indispensable role in the viral life cycle (41, 67). ICP27 is necessary for efficient expression of some E genes, including a subset of those that encode proteins required for DNA replication (83). Hence, ICP27-null mutants display a partial defect in viral DNA replication. ICP27 also promotes the expression of most L genes (11, 41, 45,62,63,67,75) and is required for the so-called delayed shutoff of host protein synthesis (19,20,67,79). How ICP27 performs its various functions remains poorly defined; however, it is becoming increasingly evident that ICP27 modulates virtually every aspect of mRNA metabolism, including primary transcription, polyadenylation, splicing, nuclear export, and mRNA stability (reviewed below).It was initially assumed that the effects of ICP27 on HSV-1 gene expression were mediated primarily at the transcriptional level. Indeed, ICP27 is required for the transcription of at least two viral l...