Sarah Dremel

Overview. We use diverse approaches - molecular virology, RNA biology, high throughput sequencing & bioinformatics - to understand how herpesviruses reshape the RNA landscape to influence infection outcomes.

Why we study herpesviruses. Our research centers on the neurotropic pathogen, Herpes Simplex Virus-1 (HSV-1), and oncovirus, Kaposi sarcoma herpesvirus (KSHV or HHV8). Herpesviruses are a major public health concern with individuals testing seropositive for at least three of the nine species by adulthood. Infection is asymptomatic for many individuals but, in cases of immune-compromise—such as transplant recipients, neonates, and those with HIV/AIDS—these viruses have devastating effects. HSV-1 commonly causes recurrent oral and genital lesions, but can also cause herpes keratitis, herpetic whitlow, and encephalitis. KSHV is an oncovirus and the causitive agent of its namesake Kaposi sarcoma. KSHV is also associated with lymphoproliferative disorders including primary effusion lymphoma (PEL) and multicentric Castleman disease (MCD). There are no FDA-approved vaccines for HSV-1 and KSHV. Additionally, we lack antivirals capable of targeting the latent reservoir and there is no therapeutic agent capable of clearing these viruses. Our research aims to identify novel biomarkers or drug targets to improve clinical diagnostics and enable development of new antiviral compounds.

Our research program. Herpesviruses have linear, double stranded, DNA genomes and replicate within the infected cell nucleus, requiring the host transcription machinery for synthesis of their >100 viral RNAs. To prioritize viral transcripts, herpesviruses affect significant changes in all stages of gene expression. This results in a drastic reshaping of the RNA landscape, including transcriptional shutoff of host Pol II transcription (mRNA), transcriptional stimulation of host Pol III transcription (tRNA), dysregulated splicing, and widespread RNA damage. These effects are coordinated by a number of viral proteins which hijack core host machinery to make the infected cell a more favorable environment for the virus.

Project 1. RNA is highly susceptible to damage via chemical (oxidative stress) or enzymatic (ribonucleases) agents which create lesions in the phosphodiester backbone. Due to RNA’s chemical structure and subcellular localization, it is significantly more vulnerable to these agents than DNA. The resulting RNA fragments must either be removed (decay, export) or repaired (RNA ligation). Our research will focus on the latter, asking the fundamental question—what is the fate of damaged RNAs which remain? We propose that in the absence of clearance, RNA damage is subject to ligation. Humans express two RNA ligases, RLIG1 and RTCB. Discovered in 2023, RLIG1 is cytoplasmic and catalyzes ligation of a 5’ phosphate and 3’ hydroxyl group. RTCB is predominantly nuclear and mediates tRNA splicing and catalyzes ligation of a 2’, 3’ cyclic phosphate or 3’ phosphate and 5’ hydroxyl group. Our research program will examine the scope and fidelity of RNA ligase-mediated repair in the context of herpesvirus infection.

Project 2. Cellular function depends on the activity of three DNA dependent RNA polymerases. RNA Polymerase I, II, and III transcribe ribosomal RNA (rRNA), messenger RNA (mRNA), and transfer RNA (tRNA), respectively. Herpesvirus infection is entirely dependent on these RNA Polymerases for synthesis of viral products and key host noncodings RNAs (rRNA, tRNA, etc). Productive HSV-1 infection is incredibly rapid, causing a single infected cell to produce progeny between 4 and 6 hours post infection, culminating in ∼1,000 infectious progeny within 18 hours. Considering the rapid HSV-1 life cycle, it is perhaps unsurprising that within 6 hours of infection, viral transcripts rise to 50% of the total mRNA within a host cell. In tandem, HSV-1 infection globally stimulates Pol III, resulting in increased Pol III transcription and accumulated ncRNA products. Within 12 hours of HSV-1 infection, total- and nascent-tRNA abundance increased 2- and 10-fold, respectively. We propose that activation of Pol III and accumulated ncRNAs (e.g. rRNA, tRNA) is required for robust productive replication. Current research is investigating the mechanism and consequences of Pol III stimulation during herpesvirus infection.

Personnel.

Tania Strilets, Postdoctoral fellow

Kathryn Harris, PhD student

Agata Kublicka, Visiting PhD student

Charlotte Wagenblast, Research technician

Caroline Mooney, Research technician

Meghan Puppala, Undergraduate researcher

Find out more.

https://www.dremel-lab.com/

https://github.com/dremellab