A triple helix stabilizes the 3 ' ends of long noncoding RNAs that lack poly(A) tails

作者：Wilusz Jeremy E^*; JnBaptiste Courtney K; Lu Laura Y; Kuhn Claus D; Joshua Tor Leemor; Sharp Phillip A

来源：Genes & Development, 2012, 26(21): 2392-2407.

DOI：10.1101/gad.204438.112

• MALAT1
• MEN beta
• NEAT1
• translation
• uridylation
• RNA decay
• RNA stability

The MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) locus is misregulated in many human cancers and produces an abundant long nuclear-retained noncoding RNA. Despite being transcribed by RNA polymerase II, the 3' end of MALAT1 is produced not by canonical cleavage/polyadenylation but instead by recognition and cleavage of a tRNA-like structure by RNase P. Mature MALAT1 thus lacks a poly(A) tail yet is expressed at a level higher than many protein-coding genes in vivo. Here we show that the 3' ends of MALAT1 and the MEN beta long noncoding RNAs are protected from 3'-5' exonucleases by highly conserved triple helical structures. Surprisingly, when these structures are placed downstream from an ORF, the transcript is efficiently translated in vivo despite the lack of a poly(A) tail. The triple helix therefore also functions as a translational enhancer, and mutations in this region separate this translation activity from simple effects on RNA stability or transport. We further found that a transcript ending in a triple helix is efficiently repressed by microRNAs in vivo, arguing against a major role for the poly(A) tail in microRNA-mediated silencing. These results provide new insights into how transcripts that lack poly(A) tails are stabilized and regulated and suggest that RNA triple-helical structures likely have key regulatory functions in vivo.

• 出版日期2012-11-1