herpes simplex virus type 1
not annotated - annotated - LINNAEUS only
20962082
The alphaherpesvirus US3/ORF66 protein kinases direct phosphorylation of the nuclear matrix protein matrin 3.
The protein kinase found in the short region of alphaherpesviruses, termed US3 in herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV) and ORF66 in varicella-zoster virus (VZV), affects several viral and host cell processes, and its specific targets remain an area of active investigation. Reports suggesting that HSV-1 US3 substrates overlap with those of cellular protein kinase A (PKA) prompted the use of an antibody specific for phosphorylated PKA substrates to identify US3/ORF66 targets. HSV-1, VZV, and PRV induced very different substrate profiles that were US3/ORF66 kinase dependent. The predominant VZV-phosphorylated 125-kDa species was identified as matrin 3, one of the major nuclear matrix proteins. Matrin 3 was also phosphorylated by HSV-1 and PRV in a US3 kinase-dependent manner and by VZV ORF66 kinase at a novel residue (KRRRT150EE). Since VZV-directed T150 phosphorylation was not blocked by PKA inhibitors and was not induced by PKA activation, and since PKA predominantly targeted matrin 3 S188, it was concluded that phosphorylation by VZV was PKA independent. However, purified VZV ORF66 kinase did not phosphorylate matrin 3 in vitro, suggesting that additional cellular factors were required. In VZV-infected cells in the absence of the ORF66 kinase, matrin 3 displayed intranuclear changes, while matrin 3 showed a pronounced cytoplasmic distribution in late-stage cells infected with US3-negative HSV-1 or PRV. This work identifies phosphorylation of the nuclear matrix protein matrin 3 as a new conserved target of this kinase group.
20980505
Translational control of the abundance of cytoplasmic poly(A) binding protein in human cytomegalovirus-infected cells.
Irrespective of their effects on ongoing host protein synthesis, productive replication of the representative alphaherpesvirus herpes simplex virus type 1, the representative gammaherpesvirus Kaposi's sarcoma herpesvirus, and the representative betaherpesvirus human cytomegalovirus [HCMV] stimulates the assembly of the multisubunit, cap-binding translation factor eIF4F. However, only HCMV replication is associated with an increased abundance of eIF4F core components (eIF4E, eIF4G, eIF4A) and the eIF4F-associated factor poly(A) binding protein (PABP). Here, we demonstrate that the increase in translation factor concentration was readily detected in an asynchronous population of HCMV-infected primary human fibroblasts, abolished by prior UV inactivation of virus, and genetically dependent upon viral immediate-early genes. Strikingly, while increased mRNA steady-state levels accompanied the rise in eIF4E and eIF4G protein levels, the overall abundance of PABP mRNA, together with the half-life of the polypeptide it encodes, remained relatively unchanged by HCMV infection. Instead, HCMV-induced PABP accumulation resulted from new protein synthesis and was sensitive to the mTORC1-selective inhibitor rapamycin, which interferes with phosphorylation of the mTORC1 substrate p70 S6K and the translational repressor 4E-BP1. While virus-induced PABP accumulation did not require p70 S6K, it was inhibited by the expression of a dominant-acting 4E-BP1 variant unable to be inactivated by mTORC1. Finally, unlike the situation in alpha- or gammaherpesvirus-infected cells, where PABP is redistributed to nuclei, PABP accumulated in the cytoplasm of HCMV-infected cells. Thus, cytoplasmic PABP accumulation is translationally controlled in HCMV-infected cells via a mechanism requiring mTORC1-mediated inhibition of the cellular 4E-BP1 translational repressor.