Figure 8
Proposed mechanisms of disruption of genome conversion of HIV-1. step 1, tRNALys3s anneal vRNA and initiate RTions, with vRNA degraded by RNaseH; step 2, strand transfer of (-)ssDNA-tRNALys3; step 3, (-)strand DNA synthesis proceeds, with vRNA degraded except for PPTs; step 4, (-)strand DNA synthesis proceeds to 5′end of vRNA; step 5, (+)strand DNA synthesis starts with complementary (mutated) PBS copied from tRNALys3; step 6: tRNALys3 is removed, and the second strand transfer fail to proceed. (A) Mechanisms by mutant tRNALys3 targeting the TAR. Both tRNALys3s are encapsidated and initiate RTions, generating two products. One primed by the mutant contain a short 5′ end of the R, but lack sequence from the 3′ end to the PBS (step 1). Following strand transfer, if it happens, synthesis of (-)ssDNA strand proceeds and degrades vRNA (step 3). Simultaneously wild-type tRNALys3-primed RTion proceeds and degrades vRNA (steps 2–6). Consequently, the integrity of vRNA is disrupted and the second strand transfer cannot proceed (step 6). For the (-)ssDNA primed by the wild-type tRNALys3, strand transfer may be blocked or proceed at lower efficiency due to lack of 5′ end of the R, and extension of the (-)DNA synthesis cannot proceed due to disrupted integrity of vRNA (step 3). (B). Mechanisms by mutant targeting sites downstream PBS. The mutant targeting the IN-coding region is taken as an example. Similar to (A), both tRNALys3s initiate RTions with vRNA degraded. The (-)ssDNA primed by mutant lack sequences beyond the PBS (step 1), which disrupts strand transfer. Extension of the (-)stand DNA synthesis by the (-)ssDNA primed by the wild-type tRNALys3 cannot proceed (step 4) due to disrupted integrity of vRNA (step 1&2), which further disrupts the second strand transfer (step 6).