Poster Presentation Australasian RNA Biology and Biotechnology Association 2024 Conference

Sequencing of nascent RNAs at single molecule resolution reveals new insights into RNA processing and modification timing. (#133)

Aditya J Sethi 1 2 3 , Marco Guarnacci 1 , Madhu Kanchi 1 , Takayuki Nojima 4 , Thomas Preiss 1 5 , Eduardo Eyras 1 2 3 , Rippei Hayashi 1
  1. The Shine-Dalgarno Centre for RNA Innovation, The John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
  2. The Centre for Computational Biomedical Sciences, The John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
  3. EMBL Australia Partner Laboratory Network at the Australian National University, Canberra, ACT 2601, Australia
  4. Research Center for Systems Immunology, Medical Institute of Bioregulation, Kyushu University, Maidashi, Fukuoka 812-8582, Japan
  5. Victor Chang Cardiac Research Institute, Sydney, NSW 2010, Australia

It is thought that much of the mRNA processing occurs co-transcriptionally. However, it remains debatable when it exactly happens relative to transcription. Here, we leverage the Nanopore direct RNA sequencing to interrogate the timing of splicing and m6A deposition during transcription in mammalian cells. We find that most of the splicing catalysis occurs after the transcription termination and cleavage. We also find that much of m6As is already deposited to unspliced nascent mRNAs. Interestingly, these m6A marks are depleted around exon junctions, suggesting that at least part of the selection of m6A deposition occurs before splicing. These observations revise the current understanding and suggest m6A deposition, transcription termination, and splicing to occur in this order in mammalian cells.