Defects in assembly explain reduced antiviral activity of the G249D polymorphism in human TRIM5a. Journal Article

Authors: Kömürlü, S; Bradley, M; Smolin, N; Imam, S; Pauszek, RF; Robia, SL; Millar, D; Nakayama, EE; Shioda, T; Campbell, EM
Article Title: Defects in assembly explain reduced antiviral activity of the G249D polymorphism in human TRIM5a.
Abstract: TRIM5a is an interferon inducible restriction factor which contributes to intrinsic defense against HIV infection by targeting the HIV capsid protein CA. Although human TRIM5a (huTRIM5a) does not potently inhibit HIV-1 infection, the ability of huTRIM5a to exhibit some control of HIV-1 infection is evidenced by a single nucleotide polymorphism in huTRIM5a which substitutes aspartic acid to glycine at position 249 (G249D) in the L2 region and is associated with higher susceptibility to HIV-1 infection. To understand the mechanistic basis for the reduced antiviral activity, we employed biophysical and cell biological methods coupled with molecular dynamics simulations to compare WT and the G249D polymorphism of huTRIM5a. We investigated the differences in conformational dynamics of rhesus and huTRIM5a Coiled Coil-Linker 2 (CC-L2) dimers utilizing circular dichroism and single molecule-Fluorescence Energy Transfer (sm-FRET). These methods revealed that the G249D dimer exhibits secondary structure and conformational dynamics similar to WT huTRIM5a. Homology modelling revealed that G249 was present on the hairpin of the antiparallel dimer, in a position which may act to stabilize the adjacent BBox2 domain which mediates the inter-dimeric contacts required for the formation of TRIM5 assemblies. We therefore asked if the G249D mutant forms assemblies in cells with the same efficiency as WT protein by expressing these proteins as YFP fusions and quantifying the number of assemblies in cells. In cells expressing comparable amounts of protein, the G249D mutant formed fewer assemblies than WT protein, in agreement with our homology modeling predictions and molecular dynamics simulations of dimers and higher oligomers of TRIM5a, providing a mechanistic explanation of the reduced antiviral activity of the G249D polymorphism.
Journal Title: PloS one
ISSN: 1932-6203; 1932-6203
Publisher: Unknown  
Date Published: 2019