Antisense transcription of the myotonic dystrophy locus yields low-abundant RNAs with and without (CAG)n repeat

RNA Biol. 2017 Oct 3;14(10):1374-1388. doi: 10.1080/15476286.2017.1279787. Epub 2017 Jan 19.

Abstract

The unstable (CTG·CAG)n trinucleotide repeat in the myotonic dystrophy type 1 (DM1) locus is bidirectionally transcribed from genes with terminal overlap. By transcription in the sense direction, the DMPK gene produces various alternatively spliced mRNAs with a (CUG)n repeat in their 3' UTR. Expression in opposite orientation reportedly yields (CAG)n-repeat containing RNA, but both structure and biologic significance of this antisense gene (DM1-AS) are largely unknown. Via a combinatorial approach of computational and experimental analyses of RNA from unaffected individuals and DM1 patients we discovered that DM1-AS spans >6 kb, contains alternative transcription start sites and uses alternative polyadenylation sites up- and downstream of the (CAG)n repeat. Moreover, its primary transcripts undergo alternative splicing, whereby the (CAG)n segment is removed as part of an intron. Thus, in patients a mixture of DM1-AS RNAs with and without expanded (CAG)n repeat are produced. DM1-AS expression appears upregulated in patients, but transcript abundance remains very low in all tissues analyzed. Our data suggest that DM1-AS transcripts belong to the class of long non-coding RNAs. These and other biologically relevant implications for how (CAG)n-expanded transcripts may contribute to DM1 pathology can now be explored experimentally.

Keywords: Antisense RNA; RAN translation; bidirectional transcription; long noncoding RNA; low-abundant RNA; microsatellite instability; myotonic dystrophy; triplet repeat expansion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Adolescent
  • Alternative Splicing
  • Case-Control Studies
  • Cell Line
  • Computational Biology / methods
  • Humans
  • Male
  • Myotonic Dystrophy / genetics*
  • Myotonin-Protein Kinase / chemistry
  • Myotonin-Protein Kinase / genetics*
  • Open Reading Frames
  • Polyadenylation
  • RNA, Antisense / chemistry
  • RNA, Antisense / genetics*
  • RNA, Long Noncoding / genetics
  • RNA, Messenger / chemistry*
  • RNA, Messenger / genetics
  • Transcription Initiation Site
  • Trinucleotide Repeat Expansion*
  • Up-Regulation

Substances

  • 3' Untranslated Regions
  • DMPK protein, human
  • RNA, Antisense
  • RNA, Long Noncoding
  • RNA, Messenger
  • Myotonin-Protein Kinase