Human JC Virus Nuclear Factor 1 Binding Motifs and Large Tumor Antigen Region Required for Transactivation of Late Promoter

Abstract

The nuclear factor 1 (NF‐1) motifs, NF‐1 II/III, in the two 98‐bp repeats of the transcription‐regulatory region of JC virus (JCV), have a critical role in brain‐specific transcription from the JCV early promoter‐enhancer. In this study, the role of these motifs in transactivation of the JCV late promoter‐enhancer (JCVL) was examined in differentiating glial P19 embryonal carcinoma cells. The expression of papovaviral large tumor antigen (T‐Ag) in the glial cells was shown by double immunofluorescence assays. By using site‐directed mutagenesis and in vivo assays, the two wild‐type NF‐1 II/III sites, but not the third site, were found to be essential for the transactivation of JCVL by JCV T‐Ag. In vitro transcription assays confirmed this specific transactivation and the transactivation was abolished by T‐Ag antibody. In electrophoretic mobility shift assays, expression of JCV T‐Ag increased the binding of a factor(s) to the 98‐bp repeat. T‐Ag antibody abolished the increase of binding. Binding assays with oligonucleotides of NF‐1 II/III motifs showed that the increased binding specifically required the wild‐type NF‐1 II/III sequences and confirmed the requirement of T‐Ag. To determine the region of T‐Ag necessary for transactivation of JCVL, the coding sequences were mutated. The amino‐terminal region of JCV Ag in amino acids 1–437 was essentially required for efficient transactivation. These results indicated that transactivation of JCVL and increased binding require a factor(s) found specifically in glial cells, the JCV NF‐1 II/III sites, and the T‐Ag amino‐terminal region.

Molecular Biology, Epidemiology, and Pathogenesis of Progressive Multifocal Leukoencephalopathy, the JC Virus-Induced Demyelinating Disease of the Human Brain

“…These sites were also shown to be more important for late gene expression (259). Additionally, these sites appear to contribute to the cell type specificity of JCV, as they are bound by different proteins in different cell types (13,14,220,259,260,409,410,483).…”

“…NFI has been shown in several studies to increase early and late gene expression in a T antigen-dependent manner (14,259,260,285), as well as to contribute to increased viral replication (344,409,410,465). The AP-1 members c-jun and c-fos have been shown to physically interact with large T antigen and suppress its activation of early genes, as well as viral DNA replication (240).…”

Transcriptional control in myelinating glia: Flavors and spices

“…Most of these cis-acting sites and corresponding trans-acting factors have been shown to regulate viral gene expression in transient transfections, with some factors influencing both viral promoters similarly, and others altering the activity of viral early and late promoters differentially (e.g., Kumar et al, 1993Kumar et al, , 1996aRanganathan and Khalili, 1993;Wegner et al, 1993a;Gallia et al, 1998). Several of these transcription factors function synergistically with JC viral T antigen (Renner et al, 1994;Kumar et al, 1996a;Gallia et al, 1998;Sock et al, 1999).…”

“…Several of these transcription factors function synergistically with JC viral T antigen (Renner et al, 1994;Kumar et al, 1996a;Gallia et al, 1998;Sock et al, 1999). Tst-1/ Oct6/SCIP has also been shown to be upregulated by T antigen in its expression possibly permitting its reactivation in mature oligodendrocytes (Renner et al, 1996b).…”

Hypoxia inducible factor-1 alpha activation of the JCV promoter: role in the pathogenesis of Progressive Multifocal Leukoencephalopathy

“…For example, YB-1 binds in close proximity to the TATA box and enhances late gene transcription [25], NF-κB, important for early and late activation [32, 42, 47], the novel DNA binding protein Pur-α, which is capable to bind to the CR and stimulate transcription of T-Antigen [15, 16], BAG-1 [11], the early growth response protein 1 or Egr-1 [45], NF-1 [30], and Smads, the downstream molecules of TGF-β [13], among others. However, there are still several other proteins that can interact with the JCV control region but remain unknown.…”