RT Journal Article
SR Electronic
T1 A conserved homo-dimerization interface in human IFIT1 provides insights into IFIT interactome assembly
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 152850
DO 10.1101/152850
A1 Yazan M. Abbas
A1 Saúl Martínez-Montero
A1 Regina Cencic
A1 Jerry Pelletier
A1 Peter D. Pawelek
A1 Masad J. Damha
A1 Bhushan Nagar
YR 2017
UL http://biorxiv.org/content/early/2017/06/21/152850.abstract
AB The Interferon-Induced Proteins with Tetratricopeptide Repeats (IFITs) are a group of potently expressed Interferon Stimulated Genes that mediate antiviral innate immunity. Previous studies have revealed that most IFITs partake in higher order structures, potentially as part of an ‘IFIT interactome’ that results in viral inhibition. Recent crystal structures of a mutated, monomeric form of IFIT1 revealed the molecular basis of how it recognizes non-self, capped viral mRNAs to selectively inhibit their translation. However, wild-type IFIT1 forms dimers in solution and the role of dimerization was not examined in detail. Here we present a structural and biochemical analysis of wild-type IFIT1 in complex with capped and uncapped RNA. Wild-type IFIT1 forms an antiparallel, elongated dimer that is in stark contrast to the domain-swapped, parallel dimer found in IFIT2. Dimerization takes place through a small, C-terminal interface that is evolutionarily conserved in IFIT1 and IFIT1B proteins. The interface is modular and can be grafted onto IFIT5, which is natively monomeric, to induce dimerization. Mutational analysis of this interface showed that homo-dimerization is not required for full RNA binding or translational inhibition by IFIT1. Sedimentation velocity analytical ultracentrifugation measurements demonstrated a reversible monomer-dimer equilibrium, suggesting that dimerization is of low affinity and could play a role under physiological concentrations, possibly in regulating IFIT interactome assembly. Finally, conformational changes in IFIT1 that occur upon RNA binding provide insight into how RNA enters its binding site in solution.