Integrase anchors viral RNA to the HIV-1 capsid interior.
Nature · 2026
In plain language
HIV-1 integrase promotes the encapsulation of viral genomic RNA into mature viral cores. The evidence comes from laboratory studies but does not directly apply to feline leukemia virus (FeLV) or cats. The same has not been demonstrated for FeLV integrase.
Scientific detail
HIV-1 integrase facilitates the encapsulation of viral genomic RNA into mature viral cores. This evidence comes from in vitro experiments and cannot be directly extrapolated to feline systems, as FeLV integrase and its function in cats are not studied.
The authors determined a cryo-EM structure of primate lentiviral integrase in complex with RNA that formed a linear filament of integrase octamer repeat units. While this is direct structural evidence, it has no implications for FeLV or clinical treatment in cats.
In the SIVtal integrase-RNA TAR cryo-EM structure, integrase tetramers engage RNA chains solely through their C-terminal domains. This does not prove that FeLV integrase has a similar domain arrangement.
HIV-1 integrase filament repeat spacing matches the mature HIV-1 capsid hexamer lattice spacing. However, this does not establish analogous capsid-integrase geometry for FeLV.
Substitutions in residues involved in HIV-1 integrase-capsid contacts produced eccentric virions, highlighting the importance of these contacts for RNA nucleoid placement within cores. This does not suggest an intervention, treatment, or clinical recommendation for FeLV.
What we know
HIV-1 integrase has been validated in studies showing its role in encapsulating viral RNA in cores. However, this research's applicability to feline leukemia is indirect, and no specific experiments have been conducted to validate its relevance in the context of FeLV.
What we don't know
No evidence supports FeLV integrase functioning similarly to that of HIV-1. Research on HIV-1 does not provide direct information about FeLV or cats, and any application to FeLV requires specific experimental validation.
Evidence
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 98/100
HIV-1 integrase promotes encapsulation of viral genomic RNA into mature viral cores.
Excerpt verified in the source — verbatim, in the source's own language“HIV-1 integrase (IN) promotes encapsulation of viral genomic RNA into mature viral cores, and this function is a target for ongoing antiretroviral drug development efforts 1-3 .”
This directly supports a role for HIV-1 integrase in genomic RNA encapsulation into mature HIV-1 cores. It does not establish the same function for FeLV integrase or any feline system.
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 98/100
The authors determined a cryo-EM structure of primate lentiviral integrase in complex with RNA that formed a linear filament of integrase octamer repeat units.
Excerpt verified in the source — verbatim, in the source's own language“Here we determined the cryogenic electron microscopy (cryo-EM) structure of a primate lentiviral IN in a complex with RNA, revealing a linear filament made of IN octamer repeat units, each comprising a pair of asymmetric homotetramers.”
This is direct structural evidence for a primate lentiviral integrase-RNA filament architecture. It is not direct evidence about FeLV, cats, clinical disease, or treatment.
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 97/100
In the SIVtal integrase-RNA TAR cryo-EM structure, integrase tetramers engage RNA chains solely through their C-terminal domains.
Excerpt verified in the source — verbatim, in the source's own language“The tetramers engage RNA chains solely through their CTDs.”
This identifies the C-terminal domains as the RNA-engaging domains in the reported SIVtal integrase-RNA structure. It does not prove that FeLV integrase uses the same domain arrangement.
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 96/100
HIV-1 integrase filament repeat spacing matches the mature HIV-1 capsid hexamer lattice spacing of 91 Å.
Excerpt verified in the source — verbatim, in the source's own language“The spacing between unit cells in the mature CA lattice (hexamers) and in the IN filament (octamers) is identical - 91 Å, as indicated by arrows.”
This supports geometric compatibility between HIV-1 integrase filaments and the mature HIV-1 capsid lattice. It does not establish analogous capsid-integrase geometry for FeLV.
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 98/100
Substitutions in residues involved in HIV-1 integrase-capsid contacts produced eccentric virions with RNA nucleoids outside the cores.
Excerpt verified in the source — verbatim, in the source's own language“Substitutions of residues involved in IN-CA contacts yielded eccentric virions with RNA nucleoids located outside of the cores.”
This supports the importance of HIV-1 integrase-capsid contacts for RNA nucleoid placement within cores. It does not establish a FeLV intervention, treatment, or clinical recommendation.
Open questionConfidence 95/100
The paper does not provide direct evidence about FeLV or cats.
The source concerns HIV-1, SIVtal/primate lentiviral integrase, cell culture systems, purified viral cores, and computational simulations. Any application to FeLV remains indirect and requires FeLV-specific experimental validation.
Provenance
Source: Integrase anchors viral RNA to the HIV-1 capsid interior.
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