Linear motif combination and not motif affinity determines displacement ability of an intrinsically disordered viral oncoprotein

CHEMES LUCÍA BEATRIZ

Telluride Colorado

Workshop; Telluride Workshop on Intrinsically Dosordered Proteins; 2017

Oak Ridge National Laboratories

In the present work, we have explored the biophysical basis for efficient disruption ofhost protein-protein interactions by a viral oncoprotein. We studied the interactionbetween the intrinsically disordered E1A protein from human adenovirus and theretinoblastoma (Rb) cellular tumor suppressor. This interaction is mediated by twohighly conserved linear motifs present within E1A, which are joined by a 70-residuelinker region. Each of these motifs binds to a distinct and highly conserved surfaceon the RbAB domain. The E1A region harboring both motifs was found to bind with1:1 stoichiometry and extremely high (KD = 24 pM) affinity to Rb. Even when theindividual viral motifs establish lower affinity interactions (KD = 140 nM) compared tothe cellular E2F counterpart (KD = 12 nM) the arrangement of two motifs joined by adisordered linker explains the effectiveness of the E1A protein, where one motif(LxCxE) acts as a docking site, increasing the effective concentration of the motif thatcompetitively displaces E2F. A simple model derived from polymer physics predictsthe compound affinity with excellent accuracy, indicating that the linker region joiningboth E1A motifs behaves as a flexible polymer of optimal length. Sequenceconservation and affinity prediction analyses reveal that disordered nature andoptimal length are highly conserved within the E1A protein family. These evidencessuggest that the effectiveness of viral proteins in disrupting the cellular network relieson both the presence of distinct motif combinations as well as on conservation offlexibility within specific viral protein regions.