Maryam Bendoumou¶
Study of the role of UHRF1 in the regulation of HIV-1 latency
Abstract¶
The latent reservoirs of the Human Immunodeficiency Virus type 1 (HIV-1) constitute the major obstacle to its eradication. HIV-1 latency is regulated by many molecular mechanisms, at the transcriptional, post-transcriptional and epigenetic level such as DNA methylation. Understanding these mechanisms would make it possible to identify new therapeutic targets and pave the way for the development of strategies aimed at eradicating the virus. In this context, our laboratory, which is particularly interested in HIV-1 latency mechanisms dependent on DNA methylation, has identified the UHRF1 factor as being recruited in vitro at the HIV-1 promoter sequence level, where the methylation status of the 5th CpG of the first island is essential for its recruitment in vitro. UHRF1 is an important epigenetic factor involved in the formation and maintenance of the heterochromatin environment through its interaction with DNMTs and histone-modifying enzymes. The latter could be involved in HIV-1 latency by maintaining a transcriptionally refractory environment at the 5' LTR promoter. In this perspective, the objective of this thesis was to investigate the functional involvement of UHRF1 in HIV-1 latency. In the first part of this thesis, we demonstrated the involvement of UHRF1 in HIV-1 latency by RNA interference. We have shown that UHRF1 depletion induces viral reactivation associated with significant demethylation of the HIV-1 5' LTR promoter. Following these results, in the second part of this thesis, we studied the functional involvement of the UHRF1 factor in the repression of HIV-1. We have shown that the repressive activity of UHRF1 against HIV-1 depends on many mechanisms both epigenetic and transcriptional. Indeed, we have shown that it is dependent on DNA methylation and that the methylation status of 5eCpG plays an important role. We have also shown that UHRF1 is able to repress Tat-mediated trans-activation, to interact with the latter and to promote its accumulation. Our results show the multiplicity and complexity of HIV-1 repressive mechanisms used by UHRF1 and place it as an attractive therapeutic target for “shock and kill” HIV-1 eradication strategies. In this context, we have shown in the third part of this thesis the ability of the phenolic compound of green tea, EGCG, to induce viral reactivation dependent on the expression of UHRF1. Together, these results, discussed in detail in this thesis, contribute to a better understanding of the molecular and epigenetic mechanisms that govern HIV-1 latency, which would ultimately allow a better understanding of the pathogenesis of HIV-1 from therapeutic perspectives.