lncRNA

Long non-coding RNAs (lncRNAs) are RNA transcripts longer than 200 nucleotides that do not encode proteins. They are transcribed by RNA polymerase II, often capped, spliced, and polyadenylated, and they comprise a substantial portion of the eukaryotic transcriptome. LncRNA expression is typically lower and more tissue-specific than that of mRNAs.

LncRNAs originate from diverse genomic contexts, including intergenic regions (lincRNAs), introns, and antisense or sense overlaps with protein-coding genes. Many localize to the nucleus where they can modulate chromatin states, while others function in the cytoplasm to influence mRNA stability or translation. Conservation across species varies, with some lncRNAs broadly conserved and others lineage-specific.

Biogenesis and processing share features with mRNAs, but lncRNA genes often have distinct promoters and splicing patterns. Some lncRNAs are produced in a time- or condition-specific manner. A subset forms circular RNAs, which are often more stable. Functional annotation remains incomplete.

Functions and mechanisms are diverse. LncRNAs can guide chromatin-modifying enzymes to specific loci, act as scaffolds for protein complexes, serve as decoys for transcription factors or microRNAs, or function as molecular signals reflecting cellular states. Classic examples include XIST in X-chromosome inactivation and MALAT1 in splicing regulation.

Biological and clinical relevance is the subject of active research. LncRNAs participate in development and physiology and have been linked to cancers, cardiovascular disease, and neurological disorders. They hold potential as biomarkers and therapeutic targets, but many lncRNAs have context-dependent roles and require rigorous validation.

Ongoing challenges include functional annotation, determining mechanisms, and translating findings across systems. Advances in sequencing, genome editing, and multi-omics are expanding our understanding of lncRNA biology and its implications for health and disease.