Interaction between the Varicella Zoster Virus IE62 Major Transactivator and Cellular Transcription Factor Sp1

Abstract

The varicella zoster virus (VZV) IE62 protein is involved in the activation of expression of all three kinetic classes of VZV proteins. Analysis of the viral promoter for VZV glycoprotein I has shown that the cellular factor Sp1 is involved in or required for the observed IE62 mediated activation. Co-immunoprecipitation experiments show that the two proteins are present in a complex in VZV-infected cells. Protein affinity pull-down assays using recombinant proteins showed that IE62 and Sp1 interact in the absence of any other viral and cellular proteins. Mapping studies using GST-fusion proteins containing truncations of IE62 and Sp1 have delimited the interacting regions to amino acids 612-778 in Sp1 and amino acids 226 -299 in IE62. The region identified in Sp1 is involved in DNA-binding, synergistic Sp1 activation, and Sp1 interaction with cellular transcription factors. The interacting region identified in IE62 overlaps with or borders on sites involved in interactions with the VZV IE4 protein and the cellular factors TBP and TFIIB. Assays using wild-type and mutant promoter elements indicate that Sp1 is involved in recruitment of IE62 to the gI promoter and IE62 enhances Sp1 and TBP binding. Varicella zoster virus (VZV)1 is a member of the alphaherpesvirinae and the causative agent of chicken pox (varicella) and shingles (zoster). The VZV genome is a linear doublestranded DNA molecule, which encodes approximately seventy proteins (1). The entire complement of VZV genes is believed to be expressed during lytic infection in three broad kinetic classes, immediate early (IE), early (E), and late (L). Transcription of VZV genes is performed by the host cell RNA polymerase II, as is the case with all other herpes viruses. Efficient expression of the VZV genome is driven by a small group of VZV gene products including those encoded by open reading frames (ORFs) 62, 4, 61, 63, and 10 (2-11). The major viral transactivator is the product of ORF 62 and its complement, ORF 71, which lie within the inverted repeats bracketing the Us region of VZV DNA. This protein is commonly designated IE62 since it is synthesized in the immediate early phase of lytic VZV gene expression. IE62 contains a potent N-terminal acidic transactivation domain and is capable of activating the expression of all three kinetic classes of VZV genes (12)(13)(14).While IE62 is involved in transactivation of VZV promoters, careful analysis of a limited number of individual viral promoters has shown that cellular transcription factors acting at sites upstream of the coding regions of the viral genes are also involved in the mechanism of IE62 activation. These proteins include the ubiquitous, sequence specific cellular factor Sp1. Sp1 is the protoype of a family of closely related factors which bind to GC-rich elements including the GC-box (GGGCGG or GGGCGGG) and the related GT/CACCC-box. Sp1 contains five distinct domains, four of which (A, B, C, and D) are involved in various aspects of transcriptional activation as well as a DNA binding region conta...

The coactivator host cell factor-1 mediates Set1 and MLL1 H3K4 trimethylation at herpesvirus immediate early promoters for initiation of infection

“…7, HCF-1 was not required for the recruitment of the RNAPII basal factor complex, which depended on the presence of the viral IE62 activator in concert with the ubiquitous cellular activator Sp1. The ability of IE62 to mediate the formation of this complex is consistent with in vitro studies indicating that IE62 interacts directly with TBP and TFIIB (26) and enhances the binding of TBP/TFIID (29). Additionally, the requirement for Sp1 for stable IE62 promoter occupancy underscores the importance of factors such as Sp1, which has been observed in studies of IE62-mediated activation (30).…”

“…In particular, stimulation of Sp1 occupancy in the presence of IE62 underscores the cooperative DNA binding suggested previously (SI Fig. 8) (29).…”

“…3). Interestingly, both IE62 and HCF-1 interact directly with Sp1 (12,29), leading to the possibility that, in addition to cooperative DNA binding interactions with IE62, Sp1 may also function to mediate or stabilize the interaction of IE62 with HCF-1. As shown in Fig.…”

Replication of varicella-zoster virus is influenced by the levels of JNK/SAPK and p38/MAPK activation

“…Downregulation of the expression of AP-1 affects the efficiency of transactivation and effectiveness of replication . Similar reports underlining the importance of specific cellular components for herpesviral gene regulation have described the physical interaction of VZV IE62 with Sp1 or USF (Peng et al, 2003; and Patel et al (1998) showed that blocking HSVmediated translocation of NF-kB into the nucleus reduced virus yields by 90 %.…”

Combinatorial Transcription of Herpes Simplex Virus and Varicella Zoster Virus Immediate Early Genes Is Strictly Determined by the Cellular Coactivator HCF-1

“…The requirement for HCF-1 in ORF10 induction of the VZV IE62 gene is consistent with in vitro studies that previously demonstrated VZV enhancer core complex assembly with Oct-1/ORF10/HCF-1 (31). However, VZV IE expression is also positively autoregulated by IE62, presumably via increasing the affinity of the TATA-binding protein (TBP) for the nonconsensus IE62 TATA element (40,41). Induction of the minimal VZV IE promoter by IE62 in an HCF-1-dependent manner suggests that HCF-1 may cooperatively facilitate this activity.…”