| Gene | Properties/function of protein |
|---|---|
| Common to All Retroviruses | |
| gag | precursor to internal structural proteins |
| pro | PR enzyme |
| pol | precursor to RT and IN enzymes |
| env | precursor to envelope glycoproteins |
| Accessory Genes | |
| HTLV/BLV (e.g., HTLV-1) | |
| tax | transcription activator |
| rex | splicing/RNA transport regulator |
| Lentiviruses (for primate lenti, e.g., HIV-1) | |
| tat | activates transcription |
| rev | regulates splicing/RNA transport |
| vif | affects infectivity of viral particles |
| vpr and/or vpx nef | is present in virion; has nuclear localization signal; facilitates infectivity in quiescent cells; triggers CD4 endocytosis, alters signal transduction in T cells; enhances virion infectivity |
| vpu | integral membrane protein; triggers CD4 degradation; enhances virion release |
| dut | dUTPase (only in nonprimate lentiviruses); facilitates replication in certain cell types |
| Type B (e.g., MMTV) | |
| sag | superantigen |
| dut | dUTPase (NC-DU fusion) |
| Type D (e.g., M-PMV) | |
| dut | DU enzyme (NC-DU fusion) |
| Spumaviruses (e.g., HSRV) | |
| bel1 | activates transcription |
| bel2 | ? |
| bet | ? |
| Piscine retroviruses (e.g., WDSV) | |
| orf A | ? |
| orf B | ? |
| orf C | ? |
From: Genetic Organization
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