Department of Microbiology & Immunology Seminar: “‘Transfer’ of Power Between Host and Herpes: tRNA Regulation in Gammaherpesvirus-Infected Cells”

Speaker:
Jessica Tucker, PhD
Assistant Professor of Microbiology and Immunology
Department of Microbiology and Immunology
Carver College of Medicine
The University of Iowa

Location: Med-Dent NE301 and via Zoom

Abstract:
Transfer RNAs (tRNAs) are fundamental to cellular and viral gene expression during infection. Recent studies have demonstrated that all three subfamilies of herpesviruses stimulate increased tRNA expression in the host. Our work profiling tRNA expression changes during murine gammaherpesvirus 68 (MHV68) infection revealed a striking accumulation of premature tRNAs (pre-tRNAs) in the late stages of infection due to a virus-induced block in pre-tRNA maturation or turnover. To examine the functional consequences of pre-tRNA upregulation on viral replication, we measured MHV68 replication during knockdown of Brf1, a transcription factor for RNA polymerase III (Pol3). Surprisingly, Brf1 knockdown leads to an enhancement of MHV68 replication, suggesting that nascent RNA polymerase III transcripts (and perhaps tRNAs) might facilitate or drive antiviral activity. Importantly, we show that Brf1-dependent antiviral activity does not require RIG-I in NIH 3T3 murine fibroblasts, ruling out a reported antiviral function of host Pol3 transcripts during herpesvirus infection. To explore other potential antiviral mechanisms, we considered whether abundant pre-tRNAs undergo cleavage into functional tRNA fragments (tRFs), as tRNA cleavage is a conserved cellular response to stress and infection. We applied state-of-the-art tRNA sequencing methodologies to profile the expression of tRNA and tRFs during MHV68 and Kaposi’s sarcoma-associated herpesvirus (KSHV) replication. We find that infection with both murine and human gammaherpesviruses trigger pre-tRNA and mature tRNA cleavage and the accumulation of specific tRFs. We are currently investigating host and viral proteins involved in infection-induced tRNA cleavage, including the role of cellular endonucleases. Finally, we are developing tools to test whether tRFs inhibit viral replication, which will expand our understanding of a conserved cellular response to infection which may be highly promising to consider in therapeutic settings.

Sponsored by the Georgetown University Department of Microbiology & Immunology