Long-Read RNA Sequencing Reveals Full-Length HERV Transcripts and Novel ERVE-4 Isoforms in Clear Cell Renal Cell Carcinoma

The challenge the researchers set out to address is technical. HERV transcripts are difficult to characterize accurately with short-read RNA sequencing because these viral elements are highly repetitive and are often spliced in noncanonical patterns. As a result, standard short-read pipelines systematically under-report which HERV elements are active in tumor cells and what transcript forms they produce.

Long-read RNA sequencing addresses these limitations by capturing full-length transcript molecules, allowing the mapping of repetitive regions and the reconstruction of complete HERV isoforms. In the study, published in Frontiers in Molecular Biosciences, the workflow identified hundreds of HERV loci in long-read datasets that were absent from the corresponding short-read annotations, demonstrating the scale of the gap left by conventional approaches.

The team applied the method to ERVE-4, a HERV element that the group had previously shown to be selectively expressed in clear cell renal cell carcinoma. ERVE-4 encodes immunogenic peptides that are currently under clinical investigation as targets for cellular immunotherapy of kidney cancer, making accurate annotation of its transcript repertoire directly relevant to ongoing therapeutic development.

The long-read analysis revealed previously uncharacterized ERVE-4 isoforms. The researchers validated the expression of these novel isoforms across multiple ccRCC tumors using RT-dPCR, a digital PCR technique that quantifies specific transcript sequences. According to the authors, these findings substantially expand the known antigenic coding potential of ERVE-4 and may imply the discovery of novel peptide targets for immunotherapy in ccRCC.

Long-read RNA sequencing improves the resolution and completeness of HERV transcriptome annotation, but the workflow was developed and demonstrated in a specific disease context, clear cell renal cell carcinoma, and its findings on ERVE-4 concern transcript discovery and validation rather than clinical efficacy. Whether the newly identified isoforms yield peptides that can be presented by tumor cells and effectively targeted in patients remains a question for future investigation.

For researchers working on the retrotranscriptome, the study offers a practical tool. The workflow, validated with short-read data, provides a way to move from fragmented, ambiguous HERV read mappings to full-length, locus-resolved transcript models.

The research, received by the journal in July 2026 and accepted in September 2026, was led by Elena A. Cherkasova and Richard W. Childs of the National Heart, Lung, and Blood Institute, with contributions from Thomas Hill and Neelam R Redekar at the National Institute of Allergy and Infectious Diseases and Stefan Barisic at Duke University School of Medicine. The authors note that all claims expressed in the article are solely their own and do not necessarily represent those of their affiliated organizations.

For kidney cancer immunotherapy in particular, the expanded catalogue of ERVE-4 isoforms provides a larger and more precisely annotated set of candidate targets for the cellular immunotherapy approaches already under clinical investigation.

Subject of Research: Long-read RNA sequencing annotation of human endogenous retrovirus transcripts and novel ERVE-4 isoforms in clear cell renal cell carcinoma

Article Title: Long-read RNA sequencing reveals full-length HERV transcripts and novel ERVE-4 isoforms with potential immunotherapeutic relevance in clear cell renal cell carcinoma

Article References: Cherkasova, E. A., Hill, T., Barisic, S., Chen, L., Diemer, J., Redekar, N., & Childs, R. W. (2026). Long-read RNA sequencing reveals full-length HERV transcripts and novel ERVE-4 isoforms with potential immunotherapeutic relevance in clear cell renal cell carcinoma. Frontiers in Molecular Biosciences, 13, Article 1941192. https://doi.org/10.3389/fmolb.2026.1941192

Image Credits: AI Generated

DOI: 10.3389/fmolb.2026.1941192

Keywords: human endogenous retroviruses, long-read RNA sequencing, ERVE-4, clear cell renal cell carcinoma, tumor-associated antigens, cellular immunotherapy, bioinformatics workflow, transcript isoforms, retrotranscriptome, splicing, kidney cancer, RT-dPCR