Alan Cochrane, University of Toronto

Jiazhen Jin1, Liang Ming1, Terek Been1, Subha Dahal1, Joshua Yang1, Stefan Aigner2,3, Gene Yeo2,3,4, and Alan Cochrane1 1Dept. of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada 2Department of Cellular and Molecular Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA 3 Institute for Genomic Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA 4Stem Cell Program, University of California San Diego, Sanford Consortium for Regenerative Medicine, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA

Suppressing & Conquering

Although current therapies prevent HIV-1 progression to AIDS, they are not a cure due to the reservoir of latently infected cells that re-establish the infection once treatment is withdrawn. Given the significant role viral RNA processing has in regulating HV-1 latency, understanding the cellular factors that maintain latency or facilitate HIV-1 gene expression is critical to our efforts to identify a cure. Toward this goal, we examined the role of SR kinases (CLK1-3) and SR proteins (SRSF1-9) in mediating the control of viral RNA processing necessary for production of all encoded proteins. While individual SR proteins/SR kinases had opposing effects on HIV-1 gene expression, the most striking finding was that several factors (CLK1, SRSF3, SRSF9) play significant roles in establishing a latent infection. Depletion of CLK1, SRSF3, or SRSF9 strongly increased HIV-1 expression by reducing the frequency of latent infections and enhanced the effect of latency reversing agents. Chromatin immunoprecipitation assays revealed association of both CLK1 and SRSF3 with the HIV-1 promoter, consistent with their role as direct repressors of HIV-1 transcription. In contrast, reduced expression of SRSF9 enhanced HIV-1 RNA synthesis without affecting HIV-1 promoter activity, suggesting it acts post-transcriptionally. In contrast, CLK2 depletion increased the frequency of latent infection due to its requirement for production of HIV-1 multiply spliced mRNAs encoding the key regulatory factors Tat and Rev. Together, these findings highlight the importance of splicing regulatory factors in the outcome of HIV-1 infection, offering novel strategies to control virus replication and manipulate the viral reservoir.