Epigenetic modification of HIV-1 Cap

Project summary Basic research opens the door to better understand, treat, and ultimately prevent existing and emerging public health threats. NIAID has prioritized fundamental research into underpinnings of the HIV-associated chronic immune activation despite the control of viral load by daily antiretroviral medication. Recent findings of the HIV-1 RNA cap hyper methylation reveal a new

paradigm of viral RNA regulation that finely tunes viral gene expression for adaptive and sustained virus replication in host immune cells. Revealing preliminary research on a new generation of HIV drug, which compromises replication of HIV clinical isolates without positive selection for drug resistance, has exposed inhibition of host TGS1 hypermethylation of HIV-1 m7G-Cap on RRE-

containing RNAs, thus establishing this small molecule will be a powerful molecular probe to investigate the molecular interactions that regulate HIV cap hypermethylation. The HIV intron- containing (ic)RNA, which contains RRE, has been reported to trigger innate immune signaling in myeloid cells, and the communications induce T cell markers of exhaustion. Preliminary data posit

the hypothesis icRNA is distinguished by its TMG-Cap, which hosts use to alleviate excessive innate immune signaling. However, it remains poorly understood how the Rev/RRE on the 3’- of viral RNA participates in the cap hyper methylation on the 5’- end. Now, by integrating ample preliminary cryoEM studies, HIV RNA-protein co-precipitations, and documentation of the

specialized translation pathway licensed by the hypermethylated HIV-1 m7G-Cap, we propose an innovative and breakthrough model that explains previous controversial observations and unclear mechanism of Rev/RRE functionality at the 5’-end of HIV-1 RNA and in translation control. Specifically, host RNA helicase A (RHA) homo-dimerizes upon binding cognate RNA structures

in the HIV-1 RNA through bipartite arrangement that tethers Rev/RRE in proximity to nuclear cap binding complex. Interdisciplinary tools are employed to delve into the basic science of the HIV TMG-Cap pathway linked to Rev/RRE. Our preliminary results posit that dysregulating the TMG- Cap pathway triggers host innate immune signaling leading to outcomes that are advantageous

for the host. The overarching project goal is to define the structural basis of the HIV cap hypermethylation regulation for viral post-transcriptional control of gene expression and define its linkage with HIV’s ability to modulate host innate immune signaling. At the project completion, the new information is expected to arm scientists for developing next-wave treatments to neutralize

deleterious immune signaling in HIV-immune cell environments.