A Single Amino Acid Change in the SPRY Domain of Human Trim5α Leads to HIV-1 Restriction

Abstract

Retroviral restriction factors are cellular proteins that interfere with retrovirus replication at a postpenetration, preintegration stage in the viral life cycle. The first restriction activity described was the mouse Fv1 gene. Three different alleles of Fv1, capable of restricting different murine leukaemia viruses (MLV), have been characterized at the molecular level. Two further activities, Ref1, which acts on MLV, and Lv1, which acts on lentiviruses, have been identified in other mammalian species. Recently, it has become clear that Ref1 and Lv1 are encoded by the same gene, Trim5alpha, which inhibits retrovirus replication in a species-specific manner. A series of chimeras between the human and rhesus monkey Trim5 genes were created to map and identify these specificity determinants. The Trim5alpha SPRY domain was found to be responsible for targeting HIV-1 restriction. By contrast, N-MLV restriction appears dependent on both the coiled-coil domain and the SPRY domain. A single amino acid substitution (R332P) in the human Trim5alpha can confer the ability to restrict HIV-1, suggesting that small changes during evolution may have profound effects on our susceptibility to cross-species infection.

Genome sequencing and comparison of two nonhuman primate animal models, the cynomolgus and Chinese rhesus macaques

“…By contrast, in the CR macaque population, the frequency of this mutation is about 50%, only marginally higher than in the IR macaque population (36%) 17 . The variation in frequency of this 6-bp deletion and of other polymorphisms between macaques of different geographic origins may well be responsible for the observed differences in HIV resistance between these macaque species/subspecies 16 . We also surveyed genetic variation in other disease-related genes in the same population of CE or CR macaques, observing that mutations often occur at different frequencies in the two species (Supplementary Section 7).…”

“…We also identified a 6-bp deletion in the TRIM5 gene in the CE macaque that results in the loss of two amino acids (Thr 339 and Phe 340 ). Recent research has indicated that deletion of these residues could lead to increased HIV or SIV pathogenicity 16 . A high frequency (97.5%) of this mutation was detected in the CE macaque population, indicating that this deletion has become virtually fixed in the CE macaque.…”

The structural biology of HIV assembly

“…TRIM5α restriction is species-and virus-specific, and the specificity of restriction is largely determined by interactions between the C-terminal SPRY/B30.2 domain and the intact retroviral capsid. Although structural details are still lacking, mutational studies and sequence analyses of different SPRY alleles have provided insights into the determinants of capsid recognition (e.g., see [138][139][140][141]). In TRIM-Cyp, the SPRY domain of TRIM5α is replaced by cyclophilin A (CypA), a well-known peptidyl prolyl isomerase.…”

“…In this case, the mechanism of capsid recognition is better understood because CA/CypA interactions have been characterized extensively. CypA makes sequence-specific contacts with the extended loop that connects CA helices 4 and 5, burying the CA Pro90 sidechain in the enzyme's active site [141,142]. Pro90 is efficiently isomerized by CypA [143], although the biological relevance of this activity remains to be determined.…”

Generation of human TRIM5α mutants with high HIV-1 restriction activity

“…33,35 In particular, substitution of TRIM5a hu arginine 332 for a proline (the aminoacid present at that position in TRIM5a rh ) decreased permissiveness to HIV-1 infection. [35][36][37] In fact, most substitutions of this residue, excepted to a lysine, resulted in significant HIV-1 restriction, showing that suppression of the positive charge was the mechanism underlying the acquisition of HIV-1 restriction potential. 36 Although the protection provided by mutations at position 332 was strong (10-to 30-fold), these mutants still restricted HIV-1 10-times less efficiently than TRIM5a rh did.…”