Adenovirus E1A down-regulates LMP2 transcription by interfering with the binding of Stat1 to IRF1

Abstract

The LMP2 gene, which encodes a protein required for efficient presentation of viral antigens, requires both unphosphorylated Stat1 and IRF1 for basal expression. LMP2 expression is down-regulated by the adenovirus protein E1A, which binds to Stat1 and CBP/p300, and by the mutant E1A protein RG2, which binds to Stat1 but not to CBP/p300, but not by the mutant protein Δ2-36, which does not bind to either Stat1 or CBP/p300. Stat1 and IRF1 associate in untreated cells and bind as a complex to the overlapping ICS- 2/GAS element of the LMP2 promoter. E1A interferes with the formation of this complex by occupying domains of Stat1 that bind to IRF1. These results reveal how adenovirus infection attenuates LMP2 expression, thereby interfering with the presentation of viral antigens.