Noncoding RNAs and the Architecture of Gene Regulation: Focus on Long and Small Regulatory RNAs.

Noncoding RNAs (ncRNAs) are a diverse and abundant class of molecules that play essential roles in gene regulation across eukaryotic organisms, including roles in human homeostasis and disease. Historically regarded as transcriptional artifacts or byproducts, ncRNAs are now recognized as essential regulators of transcriptional and post-transcriptional processes that shape cellular homeostasis and disease phenotypes. We outline the historical discovery, classification, and functional diversification of many classes of ncRNAs, with a focus on long noncoding RNAs (lncRNAs) and microRNAs (miRNAs). We summarize the current understanding of miRNA and lncRNA biogenesis, processing, and key mechanisms of action, including miRNA-lncRNA interactions and structure-dependent regulatory functions of lncRNAs. Emphasis is placed on the dynamic interplay between lncRNAs and miRNAs, their roles in fine-tuning gene expression networks, and how advances in transcriptomics, chemical probing, and structural biology have transformed our understanding of ncRNA regulatory complexity. Finally, we summarize the current landscape of RNA therapeutics. This analysis maps the historical evolution of ncRNA biology, the establishment of ncRNAs as integral regulators of gene expression and disease phenotype, and the emerging prevalence of RNA-based therapeutic strategies.