trans activation of type 1 interferon promoters by simian virus 40 T antigen.

Abstract

A human transient expression system was used to measure the influence of simian virus 40 T antigen and adenovirus Ela proteins on the activation of alpha interferon subtype 1 (IFN-a,) and IFN-1 promoters linked to the reporter chloramphenicol acetyltransferase gene. Large T-antigen production, amplified by expression plasmid replication in transfected 293 cells, was able to trans activate the IFN-, promoter 5-to 10-fold, increasing both the constitutive and Sendai virus-induced levels of expression. Surprisingly, the previously quiescent transfected IFN-ae promoter in T-antigen-expressing cells displayed a level of inducibility similar to (8,15,20,33,37). The IFN-P regulatory sequences between positions -77 and -37 relative to the mRNA CAP site comprise an inducible enhancer element, with overlapping positive and negative regulatory domains (13-15); the 5' boundary of sequences required for induction may however vary depending on the cell type (8,15). A hexanucleotide repeat (consensus AAGTGA), permutations of which are present throughout the -65 to -109 region of the IFN-P promoter, has been shown to confer virus-induced transcriptional activation to homologous or heterologous promoters (9). Similarly, an IFN-a1 promoter fragment from positions -109 to -64 conferred virus inducibility to a rabbit P-globin promoter segment (39); in addition, a GAAAGPy hexameric repeat possessed the ability to suppress the activity of constitutive enhancer elements (27). tions -68 and -38 and positions -167 to -94. After virus induction, the interferon-regulatory element-binding proteins were at least partially dissociated and replaced by a factor binding to sequences located between positions -77 and -64 (51). Similarly, a gel electrophoresis DNA-binding assay identified an IFN-specific protein in uninduced myeloid KG-1 cells interacting with the upstream region of the IFN-,B promoter (50).We previously described a human transient expression system that accurately reflected the virus-induced activation of the IFN-P promoter (49). Expression of IFN-,-Bchloramphenicol acetyltransferase (CAT) hybrid genes was dependent on induction by virus; however, no expression from the IFN-a-CAT hybrid gene was detectable, indicating that human epithelioid cells lack a factor required for the expression of the IFN-a promoter. In the present study, we demonstrate that both the IFN-P and the previously silent

Human tumor necrosis factor alpha gene regulation by virus and lipopolysaccharide.

“…Binding of the labeled probes was also blocked by the IFN-/3 promoter element PRDII (Fig. 2 A, lane 13, B, lane 6, and C, lane 7), which binds NF-KB specifically and is functionally interchangeable with the KB sequence (9,18,19). We conclude that K1, K2, and K3 can specifically bind NF-KB.…”

Synergism between Multiple Virus-induced Factor-binding Elements Involved in the Differential Expression of Interferon A Genes

“…The results obtained here with the transiently expressed IFN-A4 or IFN-A11 promoter constructs correlate well with the endogenous expression patterns of the corresponding IFN-A genes in L929 cells. In contrast, the expression of endogenous human IFN-A genes, as well as the CAT activity of the SV-CAT reporter constructs containing the human IFN-A1 promoter, were undetectable upon NDV or Sendai virus induction of HeLa cells (7,57,58). This discrepancy may be due to the presence of a negative regulatory sequence located in the human IFN-A1 promoter between the two highly conserved motifs equivalent to C and D domains of murine IFN-A4.…”

Involvement of the IRF family transcription factor IRF‐3 in virus‐induced activation of the IFN‐β gene

“…Numerous studies have focused on the mechanisms by which the IFN‐β gene is transcriptionally activated upon viral infection of the cells [1, 2]. It is well established that several cis ‐acting DNA elements exist within the promoter region of the IFN‐β gene, and that these elements bind transcription factors such as IRF‐1, IRF‐2, ISGF3, NF‐κB, AFT‐2, c‐Jun and others [5–10]. In particular, much attention has been focused on the elements which function as virus‐inducible enhancer elements, which we originally termed IRF‐Es [11].…”