lRNA

LRNA, shorthand for long regulatory non-coding RNA, refers to RNA transcripts that are typically longer than 200 nucleotides and do not encode functional proteins. Like other Pol II transcripts, they are often capped, spliced, and polyadenylated, but they lack substantial open reading frames. LRNA genes arise from intergenic regions as well as introns and antisense strands, and they display varied expression patterns, frequently exhibiting tissue- or condition-specific regulation.

LRNA functions are diverse and primarily regulatory. They can modulate chromatin state by recruiting histone modifiers, influence transcription by interacting with transcription factors, or affect post-transcriptional processes such as splicing, mRNA stability, and translation. They may act in cis to regulate neighboring genes or in trans across distant loci, often through RNA-protein interactions or by serving as molecular scaffolds.

Biogenesis and features: Most LRNA are transcribed by RNA polymerase II, with typical capping and polyadenylation; many are spliced, though some are processed differently. They tend to exhibit lower sequence conservation than protein-coding genes, but higher structural conservation in motifs or secondary structures that mediate interactions. Subcellular localization ranges from the nucleus to the cytoplasm, influencing their mode of action.

Detection and study: LRNA are identified by RNA sequencing and novel transcript annotation; their functions are investigated with loss-of-function approaches, antisense oligonucleotides, CRISPR-based repression, and RNA affinity methods to map interactions. Their expression profiles can serve as biomarkers, and perturbations are being explored for therapeutic potential, though clinical translation remains challenging.

Status and terminology: The concept of long non-coding regulatory RNA overlaps with the better-established term long noncoding RNA (lncRNA). Some sources use LRNA as an alternative label; however, lncRNA is more widely adopted. Well-characterized examples include XIST, which regulates X chromosome inactivation, illustrating the regulatory breadth of this RNA class.