Structural basis of NEAT1 lncRNA maturation and menRNA instability

NEAT1 long noncoding RNA orchestrates paraspeckle assembly and impacts tumorigenesis, fertility and immunity. Its maturation requires RNase P cleavage yielding an unstable transfer RNA-like multiple endocrine neoplasia-β tRNA-like transcript (menRNA) due to CCACCA addition. Here we report the crystal structure of human menRNA, which partially mimics tRNAs to drive RNase P and ELAC2 processing. Biophysical analyses uncover an RNA-centric, riboswitch-like mechanism whereby the nascent CCA reshapes the RNA folding landscape and propels a spontaneous conformational isomerization that directs repeat CCA addition, marking the menRNA and defective tRNAs for degradation. This study reveals the mechanisms of NEAT1 lncRNA maturation and menRNA biogenesis and uncovers an RNA-centric, riboswitch-like mechanism where menRNA drives its own conformational isomerization that directs repeat CCA addition and rapid degradation.