NcRNA

ncRNA stands for noncoding RNA, RNA transcripts that do not encode proteins. They constitute a substantial part of cellular transcripts and participate in regulation, RNA processing, and structural roles across nearly all organisms. Noncoding RNAs are commonly divided by size into small noncoding RNAs (roughly under 200 nucleotides) and long noncoding RNAs (lncRNAs, usually over 200 nt). The small class includes rRNA and tRNA, indispensable components of the ribosome and protein synthesis machinery, as well as regulatory RNAs such as microRNAs (miRNAs), small interfering RNAs (siRNAs), PIWI-interacting RNAs (piRNAs), small nuclear RNAs (snRNAs), and small nucleolar RNAs (snoRNAs) involved in RNA processing.

Long noncoding RNAs originate from diverse genomic contexts and can regulate gene expression at multiple levels. They may act as guides, scaffolds, decoys, or signals and can influence chromatin state, transcription, splicing, and mRNA stability. Some well-known lncRNAs include XIST, which mediates X-chromosome inactivation, and MALAT1 or HOTAIR, linked to transcriptional regulation and disease.

Function and study: ncRNAs operate through a variety of mechanisms, often by interacting with proteins, nucleic acids, or chromatin. Many are expressed in a tissue- or condition-specific manner, and links between ncRNAs and human disease have grown, with ongoing exploration of diagnostic and therapeutic potential. Advances in sequencing and functional genomics continue to refine ncRNA annotation and elucidate their roles in development, physiology, and pathology.