Long-read transcriptomics of caviid gammaherpesvirus 1: compiling a comprehensive RNA atlas

Caviid gammaherpesvirus 1 (CaGHV-1), formerly known as the guinea pig herpes-like virus, is an oncogenic gammaherpesvirus with a sequenced genome but an as-yet uncharacterized transcriptome. Using nanopore long-read RNA sequencing, we annotated the CaGHV-1 genome and constructed a detailed transcriptomic atlas. Our findings reveal diverse viral mRNAs and non-coding RNAs, along with mapped promoter elements for each viral gene. We demonstrated that the CaGHV-1 RTA lytic cycle transcription factor activates its own promoter, similar to Kaposi's sarcoma-associated herpesvirus (KSHV), and that the CaGHV-1 ORF50 promoter responds to RTA proteins from other gammaherpesviruses, highlighting the evolutionary conservation of RTA-mediated transcriptional mechanisms. Additionally, our analysis uncovered extensive transcriptional overlap within the viral genome, suggesting a role in regulating global gene expression. Given its tumorigenic properties, broad host range, and non-human pathogenicity, this work establishes CaGHV-1 as a promising small animal model for investigating human gammaherpesvirus pathogenesis.

The molecular underpinnings of gammaherpesvirus pathogenesis remain poorly understood, partly due to limited animal models. This study provides the first comprehensive transcriptomic atlas of CaGHV-1, highlighting both coding and non-coding RNAs and revealing regulatory elements that drive viral gene expression. Functional studies of the CaGHV-1 RTA transcription factor demonstrated its ability to self-activate and cross-activate promoters from homologous gammaherpesviruses, reflecting conserved mechanisms of transcriptional control. These findings solidify CaGHV-1 as a unique and versatile small animal model, offering new opportunities to investigate gammaherpesvirus replication, transcriptional regulation, and tumorigenesis in a controlled experimental system.