NF-κB Activation Is Delayed in Mouse L929 Cells Infected with Interferon Suppressing, but Not Inducing, Vesicular Stomatitis Virus Strains

Abstract

Vesicular stomatitis virus (VSV) mutant T1026R1 of the Indiana (IN) serotype is a good inducer of interferon (IFN). This mutant was used to study the activation of NF-kappaB, a transcription factor necessary for IFN induction, in mouse L929 cells that were stably transfected with a chimeric gene containing the human IFN-beta gene promoter attached to the chloramphenicol acetyltransferase (CAT) coding sequence. NF-kappaB DNA binding activity was detected as early as 30 min after virus adsorption in nuclear extracts, increased up to 4 hr, and then remained constant for at least 6 additional hr. The kinetics of CAT expression correlated with the kinetics of NF-kappaB nuclear DNA binding activity. Virus entry and delivery of viral components into the cytoplasm were required for NF-kappaB activation. Exposure of T1026R1 to one hit of UV irradiation nearly completely reduced NF-kappaB activation. In cells infected with wild-type (wt) VSV (IN), a noninducer of IFN, NF-kappaB DNA binding activity in the nucleus was delayed for several hours after virus adsorption. Coinfection of wt VSV and T1026R1 resulted in the reduction of T1026R1-promoted NF-kappaB activation. This inhibitory activity of wt VSV was abolished by one hit of UV irradiation. Under similar conditions expression of the CAT gene was more UV resistant, suggesting that IFN gene expression is regulated at multiple levels.

Ability of the Matrix Protein of Vesicular Stomatitis Virus To Suppress Beta Interferon Gene Expression Is Genetically Correlated with the Inhibition of Host RNA and Protein Synthesis

“…However, it is also possible that M protein inhibits additional steps in the production of IFNs upstream of the general transcription factor TFIID. For example, the activation of NF-B, one of the factors required for IFN gene transcription, is delayed in cells infected with wt VSV compared to cells infected with the T1026R1 mutant (8). This suggests that the wt M protein delays activation of NF-B, which could play a role in the suppression of IFN gene expression.…”

Cytopathogenesis and Inhibition of Host Gene Expression by RNA Viruses

“…However, in cells capable of producing and responding to alpha/beta interferons, such as chicken embryo cells, the replication of these viruses is severely compromised, particularly at elevated temperatures, so that one of these mutants (tsO82) was originally identified as a ts mutant (40). Infection with viruses containing M gene mutations, such as tsO82 virus, results in production of much more alpha/beta interferon than does infection with the wild-type viruses from which they were derived (15,89), supporting a role for M protein in suppressing the induction phase of the alpha/beta interferon response. There is one example of a VSV mutant in which infected cells produce more alpha/beta interferon than do cells infected with the wild-type strain from which this mutant was derived, yet this mutant does not contain a mutation in its M protein (89).…”

The vesicular stomatitis virus matrix protein inhibits NF-κB activation in mouse L929 cells

“…A previous report indicated that NF-κB activation is delayed for several hours after wild-type (wt) vesicular stomatitis virus (VSV) infection, while this transcription factor is rapidly activated in L929 cells infected with the T1026R1 (R1) mutant strain of VSV (Boulares et al, 1996). The R1 virus (Stanners et al, 1977) expresses a mutant matrix (M) protein, in which there is methionine-to-arginine substitution at amino acid position 51 (Ferran and Lucas-Lenard, 1997).…”