NLM DIR Seminar Schedule

Abstract:

Covalently closed circular RNAs (cccRNA) are involved in various cellular processes and are the genomic template of viroids and viroid-like elements such as Ribozyviria (including Hepatitis Delta Virus, HDV), virusoids, ambiviruses or the recently discovered obelisks. Although their presence across eukaryotes and archaea and as infectious agents, their abundance as well as variety is far from being understood, including completely undiscovered entities as seen with recently discovered obelisks.
I will present our preliminary results characterizing nearly 9 million putative cccRNA found in (meta)transcriptomic data by a recently developed pipeline in our group. The majority of cccRNAs is rather small with 75% below 250 nt but largest ones are thousands of nucleotides long. Predicting open reading frames revealed nearly 5 million encoding for putative proteins of at least 60 aa. Subsequent protein clustering, annotation and structure prediction of proteins encoded by at least two independent cccRNAs was used to characterize the putative proteins. Putative cellular proteins encoded by cccRNAs were linked to their likely cellular role by KEGG pathways annotation and putative viral proteins were examined. Interestingly, a handful of putative proteins encoded by at least 10 cccRNAs showed good structure prediction and a globular fold but no relationship with known proteins, indicating the presence of newly discovered cccRNA entities. To classify the cccRNA itself, we started to predict RNA secondary structures to identify abundant folds which can represent new classes of Ribozymes.