Adenovirus E1A binding to DCAF10 targets proteasomal degradation of RUVBL1/2 AAA+ ATPases required for quaternary assembly of multiprotein machines, innate immunity, and responses to metabolic stress

Abstract

ABSTRACT Adenovirus small e1a protein modifies host cell physiology to optimize virus replication. The N-terminal ~140 aa of e1a interacts with RB-family proteins to derepress dNTP and DNA synthesis and with EP300/CREBBP lysine acetyltransferases and EP400-TIP60 chromatin-modifying complexes to inhibit host anti-viral innate immune responses. However, the e1a N-terminal region activates a late host anti-viral response due to stabilization and activation of IRF3. The E1A C-terminal region counteracts IRF3 stabilization through interactions with three host nuclear proteins with seemingly unrelated functions. All three C-terminal interactions are required for e1a-association into a multi-protein complex with scaffold subunits of a CRL4 E3 ubiquitin ligase and DCAF10, a presumed specificity subunit. This e1a-DCAF10-CRL4 prevents IRF3 stabilization indirectly by targeting the essential AAA+ ATPases RUVBL1/2, subunits of several HSP90 co-chaperones required for quaternary assembly of cellular protein machines required for anti-viral defenses and responses to genotoxic and metabolic stress. IMPORTANCE Inactivation of EP300/CREBB paralogous cellular lysine acetyltransferases (KATs) during the early phase of infection is a consistent feature of DNA viruses. The cell responds by stabilizing transcription factor IRF3 which activates transcription of scores of interferon-stimulated genes (ISGs), inhibiting viral replication. Human respiratory adenoviruses counter this by assembling a CUL4-based ubiquitin ligase complex that polyubiquitinylates RUVBL1 and 2 inducing their proteasomal degradation. This inhibits accumulation of active IRF3 and the expression of anti-viral ISGs, allowing replication of the respiratory HAdVs in the face of inhibition of EP300/CBEBBP KAT activity by the N-terminal region of E1A.