Talk abstracts

Talk on Friday 01:45-02:00pm submitted by Ioana Boeras

HIV-1 requires two non-redundant functions of host RNA helicase A: helicase activity for mRNA translation and chaperone activity for virion replication

Ioana Boeras (Department of Veterinary Biosciences, Center for Retrovirus Research, Center for RNA Biology, Ohio State University, Columbus Ohio, USA), Kathleen Boris-Lawrie (Department of Veterinary Biosciences, Center for Retrovirus Research, Center for RNA Biology, Ohio State University, Columbus Ohio, USA)

Abstract:
The functional repertoire of RNA helicases is immense, facilitating the RNA biology of eukaryotic cells and the viruses that infect them. Proteomic approaches have identified host RNA helicases that interact with the cis-acting replication sequences of several retroviruses including HIV-1. Functional assays determined DHX9/RNA helicase A (RHA) specifically and selectively recognizes cis-acting replication elements in the 5’ terminus. Downregulation of RHA impairs the efficient translation of viral mRNAs. Domain analysis demonstrated N-terminal residues of RHA are necessary for RHA’s specific recognition of the cognate viral RNA. Polyribosome analysis determined N-term tethers RHA’s ATPase-dependent helicase domain to catalyze efficient translation. Beyond the catalytic activity, RHA also provides chaperone activity that promotes the infectivity of progeny virions. RHA is incorporated into HIV-1 virions and its stoichiometry of ~2 RHA molecules per particle is in proportion to the viral genomic RNA (n=2). RHA-deficient virions are produced by siRNA downregulation or by deletion of the RHA-responsive elements in the 5’ RNA terminus, indicating incorporation of RHA is viral RNA-dependent. Unexpectedly, the ATPase-deficient RHA allele rescues viral infectivity, demonstrating that a nonenzymatic activity of RHA is sufficient to propagate infectious virions. RHA domains necessary for incorporation into HIV-1 particles have been tested for their ability to rescue infectivity. Results suggest the ability of RHA to bind cognate viral RNA and to form a homodimer is necessary to bolster infectivity. Our results demonstrate two non-redundant functions of RHA are directed by viral RNA elements: ATP-dependent helicase and RNA chaperone activity promote the quality of the viral RNA-protein complex to bolster viral replication.

Keywords: RNA helicase A