Hsc70 Focus Formation at the Periphery of HSV-1 Transcription Sites Requires ICP27

The cellular chaperone protein Hsc70, along with components of the 26S proteasome and ubiquitin-conjugated proteins have been shown to be sequestered in discrete foci in the nuclei of herpes simplex virus 1 (HSV-1) infected cells. We recently reported that cellular RNA polymerase II (RNAP II) undergoes proteasomal degradation during robust HSV-1 transcription, and that the immediate early protein ICP27 interacts with the C-terminal domain and is involved in the recruitment of RNAP II to viral transcription/replication compartments.Here we show that ICP27 also interacts with Hsc70, and is required for the formation of Hsc70 nuclear foci. During infection with ICP27 mutants that are unable to recruit RNAP II to viral replication sites, viral transcript levels were greatly reduced, viral replication compartments were poorly formed and Hsc70 focus formation was curtailed. Further, a dominant negative Hsc70 mutant that cannot hydrolyze ATP, interfered with RNAP II degradation during HSV-1 infection, and an increase in ubiquitinated forms of RNAP II was observed. There was also a decrease in virus yields, indicating that proteasomal degradation of stalled RNAP II complexes during robust HSV-1 transcription and replication benefits viral gene expression.We propose that one function of the Hsc70 nuclear foci may be to serve to facilitate the process of clearing stalled RNAP II complexes from viral genomes during times of highly active transcription

Increased template activity of liver chromatin, a result of hydrocortisone administration.

We have found that the administration of hydrocortisone to adrenalectomized rats increases the template activity of their liver chromatin for RNA synthesis. Such administration is known to cause a two- to threefold increase in rate of nuclear RNA synthesis in the liver (1,2). This increase is followed by an increase in the activities of a series of liver enzymes (3-5). Since the induction of these enzymes by hydrocortisone is abolished by simultaneous treatment with actinomycin D, it is clear that new RNA synthesis is required to support their formation (4,5). The increased rate of liver RNA synthesis caused by administration of hydrocortisone might in principle be due to changes in the template activity of the liver genetic material such as would accompany derepression of genes previously repressed. We shall show below that the administration of hydrocortisone does result in an increased availability of the genetic material for transcription