Histone Deacetylases 1 and 2 Are Phosphorylated at Novel Sites during Varicella-Zoster Virus Infection

Abstract

ORF66p, a virion-associated varicella-zoster virus (VZV) protein, is a member of a conserved Alphaherpesvirinae kinase family with homology to herpes simplex virus U S 3 kinase. Expression of ORF66p in cells infected with VZV or an adenovirus expressing only ORF66p results in hyperphosphorylation of histone deacetylase 1 (HDAC1) and HDAC2. Mapping studies reveal that phosphorylation is at a unique conserved Ser residue in the C terminus of both HDACs. This modification requires an active kinase domain in ORF66p, as neither protein is phosphorylated in cells infected with VZV lacking kinase activity. However, hyperphosphorylation appears to occur indirectly, as within the context of in vitro kinase reactions, purified ORF66p phosphorylates a peptide derived from ORF62p, a known substrate, but does not phosphorylate HDAC. These results support a model where ORF66p is necessary but not sufficient to effect hyperphosphorylation of HDAC1 and HDAC2.

Hyperphosphorylation of Histone Deacetylase 2 by Alphaherpesvirus US3 Kinases

“…In addition, autonomous expression of HSV-1 US3 and US3.5 resulted in enhanced expression of viral or cellular genes, similar to what occurs in cells treated with sodium butyrate, a pan-tropic HDAC inhibitor (43,45). Treatment of cells with sodium butyrate also partially complements the growth defect associated with a VZV mutant lacking ORF66p kinase activity (61). These studies suggest a mechanism whereby US3 kinasemediated hyperphosphorylation of HDAC1 and HDAC2 inhibits their repressive activity to allow efficient gene expression and viral replication.…”

“…Phosphorylation of HDACs is the most extensively studied modification, and reports have shown that enzy-matic activity, cellular localization, and protein-protein interactions of HDACs are regulated in this manner (reviewed in reference 18). HDAC1 and HDAC2 are hyperphosphorylated during HSV-1, HSV-2, and VZV infection in a US3 kinasedependent manner (26,39,43,61). In addition, autonomous expression of HSV-1 US3 and US3.5 resulted in enhanced expression of viral or cellular genes, similar to what occurs in cells treated with sodium butyrate, a pan-tropic HDAC inhibitor (43,45).…”

Viral Serine/Threonine Protein Kinases

“…This is in contrast to findings for HSV-1 and VZV and indicates virus-specific US3-independent mechanisms of HDAC hyperphosphorylation. Inhibition of HDAC activity increased plaquing efficiency of US3-null virus for PRV and VZV, but not for HSV-1, pointing to virus-and celldependent differences in the functional significance of US3-mediated HDAC modification (223,224). …”

“…Over the last couple of years, it has become evident that US3 also affects gene expression. US3 orthologs of HSV-1, HSV-2, PRV, and VZV phosphorylate HDAC1 and -2, thereby inhibiting the deacetylation of histones, which otherwise silence gene expression (151,176,223,224). US3-mediated phosphorylation of HDAC2 occurs at a C-terminally located conserved serine residue (224).…”

“…US3-mediated phosphorylation of HDAC2 occurs at a C-terminally located conserved serine residue (224). HSV-1 US3 is able to phosphorylate HDAC-1 and -2 directly (177, 178), although there are indications that VZV, PRV, and HSV-1 phosphorylate HDAC indirectly by activating a cellular kinase pathway (223,224). For PRV, hyperphosphorylation of HDAC2 was still observed in cells infected with a US3-null recombinant (224).…”