Species-Specific Variation in the B30.2(SPRY) Domain of TRIM5α Determines the Potency of Human Immunodeficiency Virus Restriction

Abstract

Retroviruses encounter dominant postentry restrictions in cells of particular species. Human immunodeficiency virus type 1 (HIV-1) is blocked in the cells of Old World monkeys by TRIM5␣, a tripartite motif (TRIM)protein composed of RING, B-box 2, coiled-coil, and B30.2(SPRY) domains. Rhesus monkey TRIM5␣ (TRIM5␣ rh ) more potently blocks HIV-1 infection than human TRIM5␣ (TRIM5␣ hu ). Here, by studying chimeric TRIM5␣ proteins, we demonstrate that the major determinant of anti-HIV-1 potency is the B30.2(SPRY) domain. Analysis of species-specific variation in TRIM5␣ has identified three variable regions (v1, v2, and v3) within the B30.2 domain. The TRIM5␣ proteins of Old World primates exhibit expansion, duplication, and residue variation specifically in the v1 region. Replacement of three amino acids in the N terminus of the TRIM5␣ hu B30.2 v1 region with the corresponding TRIM5␣ rh residues resulted in a TRIM5␣ molecule that restricted HIV-1 nearly as efficiently as wild-type TRIM5␣ rh . Surprisingly, a single-amino-acid change in this region of TRIM5␣ hu allowed potent restriction of simian immunodeficiency virus, a phenotype not observed for either wild-type TRIM5␣ hu or TRIM5␣ rh . Some of the chimeric TRIM5␣ proteins that are >98% identical to the human protein yet mediate a strong restriction of HIV-1 infection may have therapeutic utility. These observations implicate the v1 variable region of the B30.2(SPRY) domain in TRIM5␣ rh antiviral potency.The primate lentiviruses include human immunodeficiency virus type 1 (HIV-1) and HIV-2 and simian immunodeficiency viruses (SIVs) (2,5,7,8,11). HIV-1 and HIV-2 infect humans, HIV-1-like viruses infect chimpanzees, and SIV variants infect African monkeys. Humans infected by HIV-1 and HIV-2 and Asian macaques infected by certain SIV strains (SIV mac ) often develop life-threatening immunodeficiency due to depletion of CD4-positive T lymphocytes (9,19).HIV and SIV tropism is determined by cell-type-specific and species-specific host factors. Following entry into the host cell, uncoating of the viral core, reverse transcription, nuclear access, and integration of the viral DNA into the host genome must occur to establish a permanent infection (1,10,33). Early postentry restrictions to retrovirus infection can determine tropism at the species level. HIV-1 encounters a postentry block in Old World monkeys, whereas SIV mac is blocked in most New World monkey cells (15,16,27). These species-specific restrictions occur prior to or concurrent with reverse transcription; at most, low levels of early reverse transcripts are made in restricted cells (6,15,20,27). The viral determinant of susceptibility to these blocks is the capsid protein (6,13,18,22,23,30). The early restriction of HIV-1 and SIV is mediated by dominant host factors, the activities of which can be titrated by the introduction of virus-like particles containing proteolytically processed capsid proteins of the restricted viruses (3,4,6,12,22,31,32). Thus, in the cells of specific monkey species, host restricti...

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.…”

“…Although the subsequent events that lead to restriction are not yet well understood, TRIM5α and TRIMCyp typically prevent accumulation of reverse transcripts (although later-stage blocks are observed under some restricting conditions [146,147]). TRIM5α restriction correlates with accelerated rates of retroviral capsid dissociation, leading to the proposal that TRIM5α (and its cofactors) destabilize the capsid before it can perform essential functions [138,148]. Alternatively, TRIM5α may inactivate cores by diverting them to cytoplasmic "TRIM bodies" and/or to the proteasome (e.g., see ref.…”

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

“…For instance, TRIM5a rh with an arginine at this position instead of a leucine was still fully able to restrict HIV-1. 35 Li et al 36 constructed the reciprocate R335L mutation of TRIM5a hu and found that it weakly inhibited HIV-1; in addition, the double-mutant R332P/ R335L restricted HIV-1 less efficiently than R332P alone. Therefore, isolation of an Arg335 mutant in our screen was rather unexpected.…”

“…33,34 Versions of human TRIM5a in which short stretches of the v1 region were replaced by those of the macaque orthologue showed restriction activity against HIV-1. 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.…”

“…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.…”