Characterization of interferon-alpha 13, a novel constitutive murine interferon-alpha subtype.

Viruses and cell culture. Viruses used in this study were Theiler's virus DA1 and its L cys mutant, TM598, carrying two Cys to Arg mutations disrupting the zinc finger of the L protein (29,30). The KJ6 and TM659 are the corresponding wild-type and L cys -mutant viruses carrying a capsid adapted to infect L929 cells (29,31). These viruses were by transfection of BHK-21 cells with viral RNAs in from the infectious cDNA clones, pTMDA1, pTM598, pKJ6, pTM659 (29). An strain of Mengo virus was produced in a similar way from the pMC16 infectious clone (32). Paris). were titrated cells standard plaque assay. IFN- a 4 was the predominant subtype induced in primed cells following infection with both the wild-type and the L-mutant viruses. The proportion of IFN- a 13 or of IFN pseudogenes transcripts strongly decreased after priming, showing that these genes are unresponsive to IRF-7, contrary to the other IFN- a subtypes. a transcription in uninfected IFNAR-1-/- MEFs at levels comparable to that seen in uninfected wild-type cells. Significantly, MEFs deficient for both IRF-3 and IRF-9 still transcribe constitutive IFN- a, while induction of IFN- a/b following NDV infection is abolished in these cells. Taken together, these results show constitutive IFN transcription is independent of the factors that regulate virus inducibility of the IFN- a promoters.