Ydrnas

Ydrnas is a term used in some genomic and transcriptomic studies to describe a proposed class of non-coding RNA transcripts detected in eukaryotes, most notably in yeast. The label is not yet universally adopted and its exact definition varies by study. In many descriptions, ydrnas refer to RNA species that are transcribed from intergenic or antisense regions and exhibit little or no protein-coding potential. They are typically identified by high-throughput RNA sequencing and exhibit stable presence across samples or conditions, though distinguishing functional transcripts from transcriptional noise remains challenging.

Biogenesis and structure: Ydrnas are thought to originate primarily through pervasive transcription or read-through from nearby promoters, and they may be produced by canonical RNA polymerase II machinery. Some transcripts show features of processing or maturation, while others appear as unstable, rapidly degraded RNAs. They commonly lack conserved open reading frames and show variable exon-intron structures across species.

Potential functions: Proposed roles include regulation of neighboring gene expression through transcriptional interference, involvement in chromatin modification, or participation in RNA-based regulatory networks. However, empirical functional validation is limited, and many researchers view ydrnas as potentially including non-functional transcriptional byproducts.

Relation to other RNAs: Ydrnas are considered distinct from canonical mRNAs, miRNAs, siRNAs, and well-characterized long non-coding RNAs, though overlaps with antisense transcripts and promoter-associated RNAs have been reported.

As a field, the study of ydrnas remains ongoing, with debates about their prevalence, significance, and criteria for functional designation.