The host-cell architectural protein HMG I(Y) modulates binding of herpes simplex virus type 1 ICP4 to its cognate...

The productive infection cycle of herpes simplex virus is controlled in part by the action of ICP4, an immediate-early gene product that acts as both an activator and repressor of transcription. ICP4 is autoregulatory, and IE-3, the gene that encodes it, contains a high-affinity binding site for the protein at its cap site. Previously, we had demonstrated that this site could be occupied by proteins found in nuclear extracts from uninfected cells. A HeLa cell cDNA expression library was screened with a DNA probe containing the IE-3 gene cap site, and clones expressing the architectural chromatin proteins HMG I and HMG Y were identified by this technique. HMG I is shown to augment binding of ICP4 to its cognate site in in vitro assays and to enhance the activity of this protein in short-term transient expression assays.