Disordered Motifs and Domains in Cell Control - October 11-15, 2014

Disordered Motifs and Domains in Cell Control

Poster Session I

24-POS Board 24 Binding Properties of Linear Motif-mediated Viral Retinoblastoma-target Protein Interactions Lucía B. Chemes 1 , Nicolás González Foutel 1 , Gonzalo de Prat Gay 1 1 Leloir Institute-IIBBA CONICET Av. Patricias Argentinas Many proteins from pathogenic viruses have intrinsically disordered (IDP) domains harboring short linear motifs that target cellular functions. The LxCxE and E2F motifs mediate high- affinity binding to the retinoblastoma (Rb) tumor suppressor, promoting cell cycle progress and efficient replication of the viral genome. However, persistent expression of viral proteins can lead to cell transformation and cancer. Interference with host functions is key to understanding viral pathogenesis. However, current insight into structure-function relationships of viral proteins is still scarce. A review of experimentally reported instances revealed LxCxE and E2F motifs presence in viral and cellular partners. However, viral instances are located exclusively within IDP regions and enriched in sequence features enhancing binding affinity, suggesting they may have evolved to allow for effective competition with cellular interactions. Cellular instances are located in exposed loops or helices, suggesting a stronger entropic cost for binding. Solution binding studies of the LxCxE and E2F motifs from four cellular and viral Rb targets showed that the E2F2 transcription factor motif bound Rb with high affinity ( K D = 12 nM). Opposed to the two-state behavior of the HPV E7 LxCxE site, binding involves slow conformational rearrangements of the E2F2 motif. The individual LxCxE and E2F motifs from the adenovirus E1A protein presented K D values in the 200 nM range, suggesting that the full-length protein has sub-nanomolar affinity and that both E1A and HPV E7 compete effectively for binding with the low affinity ( K D = 10 µM) histone deacetylase protein. These results suggest that intrinsic disorder may favor the evolution of both conformational and sequence features within viral linear motifs, endowing viral proteins with high affinity interactions that interfere effectively with host functions, and stress the need for a combined structure-function and evolutionary analysis of pathogenic virus-host interactions.

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