Poster de conférence
Résumé : There is increasing evidence for the physiological relevance of myeloid HIV-1 reservoirs such as brain microglia and urethral macrophages. However, the molecular mechanisms of HIV-1 gene expression in myeloid infected cells are still poorly understood. The HIV-1 intragenic cis-regulatory region (IRR) located in the pol gene exhibits an enhancer activity on the 5’LTR promoter. The IRR possesses multiple binding sites for various cellulartranscription factors. Here, we characterized several of these binding sites and their functional involvement in the IRR-mediated control of HIV-1 gene expression in monocytes/macrophages. Special emphasis was put on studying several binding sites for the myeloid-specific transcription factor PU.1, known to be a pioneer transcription factor inducing the opening of heterochromatin in enhancers.We demonstrated the in vivo recruitment of PU.1 to the HIV-1 intragenic enhancer in latently-infected cell lines from myeloid origin. We physically characterized in vitro PU.1 binding to the different intragenic PU-boxes and identified mutations abolishing PU.1 binding without altering the underlying amino acid sequence of the pol gene. We demonstrated the role of thePU-boxes in the enhancer activity of the IRR and in its epigenetic profile in latency and reactivated conditions, in concert with other IRR transcription factor binding sites. We showed the importance of intragenic transcription factor binding sites in HIV-1 replication using mutated viral particles in single-round infection experiments using primary monocytes-derived macrophages isolated from uninfected individuals. To overcome HIV- 1 persistence, targeted approaches for each specific reservoir are needed. As a proof-of-concept, we revealed the potential therapeutic application of a specific inhibitor interfering with PU.1 binding used in the highly relevant model of monocyte-derived macrophages as a new anti-HIV-1 approach.The HIV-1 intragenic enhancer brings an additional factor in an already complex network of regulators affecting the level of HIV-1 transcription. Such complexity could allow a finer-tuned regulation that might find its purpose when HIV-1 transcription needs to be moderately or transiently modified within different cellular and chromatin environments. The role of the IRR in HIV-1 gene expression regulation opens new avenues for HIV cure approaches targeting the heterogeneous cellular and tissue latent reservoirs of virus.

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