RNAturnover

RNATurnover, or RNA turnover, refers to the regulated balance between RNA synthesis and RNA degradation that determines the abundance of RNA molecules in a cell. This process integrates transcriptional control with post-transcriptional decay to shape gene expression in a dynamic way. While turnover is commonly discussed in the context of messenger RNAs (mRNAs), it also applies to noncoding RNAs such as rRNA, tRNA, and numerous regulatory RNAs, each with characteristic stability.

In eukaryotes, RNA turnover proceeds through coordinated decay pathways. A typical mRNA lifeline begins with deadenylation, the shortening of the poly(A) tail, followed by decapping and degradation from the 5′ end by the exonuclease XRN1, or from the 3′ end by the exosome complex. Specialized pathways add regulatory complexity: AU-rich element-mediated decay targets specific transcripts; nonsense-mediated decay eliminates RNAs with premature stop codons; and microRNA- or siRNA-guided decay modulates many transcripts post-transcriptionally. Decay rates vary widely among transcripts and tissues, yielding a spectrum of mRNA half-lives from minutes to hours, and contributing to rapid adaptation to stimuli.

Measuring turnover combines transcriptional and labeling approaches. Turnover rates are inferred from RNA half-life estimates using metabolic labeling, transcriptional inhibition, or sequencing-based methods such as BRIC-seq or SLAM-seq. Turnover is influenced by developmental stage, cell type, stress conditions, and disease states. Aberrations in RNA stability are linked to cancer, neurodegenerative disorders, and immune responses. Understanding RNATurnover provides insight into how cells orchestrate gene expression and respond to changing environments.