Interaction of herpes simplex virus 1 alpha regulatory protein ICP0 with elongation factor 1delta: ICP0 affects translational machinery

Abstract

The herpes simplex virus 1 (HSV-1)-infected cell protein 0 (ICP0) is a promiscuous transactivator, and by necessity, its functions must be mediated through cellular gene products. In an attempt to identify cellular factors interacting with ICP0, we used the carboxyl-terminal domain of ICP0 as "bait" in the yeast (Saccharomyces cerevisiae) two-hybrid system. Our results were as follows: (i) All 43 cDNAs in positive yeast colonies were found to encode the same translation factor, elongation factor delta-1 (EF-1␦). (ii) Purified chimeric protein consisting of glutathione S-transferase (GST) fused to EF-1␦ specifically formed complexes with ICP0 contained in HSV-1-infected cell lysate. (iii) Fractionation of infected HEp-2 cells and immunofluorescence studies revealed that ICP0 was localized both in the nucleus and in the cytoplasm. In primary human foreskin fibroblasts, ICP0 was localized predominantly in the cytoplasm throughout HSV-1 infection even early in infection. (iv) Addition of the chimeric protein GST-carboxyl-terminal domain of ICP0 to the rabbit reticulocyte lysate in vitro translation system resulted in a dose-dependent decrease in protein synthesis. In contrast, GST alone or GST fused to the amino-terminal domain of ICP0 had no effect on the in vitro translation system. (v) The predominant forms of EF-1␦ on electrophoresis in denaturing gels have apparent M r s of 38,000 and 40,000. The higher-M r form is a minor species in mock-infected cells, whereas in human fibroblasts and Vero cells infected with HSV-1, this isoform becomes dominant. These results indicate that ICP0 is present and may have a significant role in the cytoplasm of infected cells, possibly by altering the efficiency of translation of viral mRNAs.

Mutational analysis of the herpes simplex virus type 1 ICP0 C3HC4 zinc ring finger reveals a requirement for ICP0 in the expression of the essential alpha27 gene

“…This discordance between the presence of ␣27 RNA and the absence of protein reinforces our hypothesis that ICP0 regulates the production of ICP27. This hypothesis is consistent with the observation that ICP0 interacts with EF-1␦, a major translational regulatory factor (39). The experiments we have described also demonstrate that deleterious mutations in ICP0 affect the accumulation of IE RNAs at late times postinfection.…”

Protein kinases conserved in herpesviruses potentially share a function mimicking the cellular protein kinase cdc2

“…EF-1 is a component of the EF-1 complex responsible for GDP-GTP exchange on EF-1 [61][62][63][64]. An HSV-1 regulatory protein, ICP0, interacts with EF-1; the interacting domain of ICP0 affects translational efficiency in vitro [65]. A regulatory protein encoded by type 1 human immunodeficiency virus, Tat, whose amino acid sequence shows a weak but significant similarity to ICP0, also interacts with EF-1 to shut-off host cell mRNA translation [66].…”

ICP0, a regulator of herpes simplex virus during lytic and latent infection

“…In addition, some published information implies that ICP0 might have other functions in addition to the induction of specific cellular protein instability. These include interaction with other viral regulatory molecules, (60) with the translation mechanism (61) and with cyclin D3. (62) Time will tell where these observations fit into the picture.…”