Talk abstracts

Talk on Saturday 03:15-03:30pm submitted by Daniel del Valle-Morales

Inhibition of cytoplasmic cap methylation identifies 5’ TOP mRNAs as recapping targets and reveals recapping sites downstream of native 5’ ends

Daniel del Valle-Morales (Center for RNA Biology, Department of Biological Chemistry and Pharmacology, Molecular, Cellular and Developmental Biology Program, The Ohio State University), Jackson B. Trotman (Center for RNA Biology, Department of Biological Chemistry and Pharmacology,The Ohio State University), Ralf Bundschuh (Center for RNA Biology, Department of Physics,Division of Hematology, The Ohio State University), Daniel R. Schoenberg (Center for RNA Biology, Department of Biological Chemistry and Pharmacology, The Ohio State University)

Abstract:
Cap homeostasis is the cyclical process of decapping and recapping that maintains the translation and stability of a subset of the transcriptome. Previous work showed levels of some recapping targets decline following transient expression of an inactive form of RNMT (ΔN-RNMT), likely due to degradation of mRNAs with improperly methylated caps. The current study examined transcriptome-wide changes following inhibition of cytoplasmic cap methylation. This identified mRNAs with 5’-terminal oligopyrimidine (TOP) sequences as the largest single class of recapping targets. Cap end mapping of several TOP mRNAs identified recapping events at native 5’ ends and downstream of the TOP sequence of EIF3K and EIF3D. This provides the first direct evidence for downstream recapping. Inhibition of cytoplasmic cap methylation was also associated with mRNA abundance increases for a number of transcription, splicing, and 3’ processing factors. Previous work suggested a role for alternative polyadenylation in target selection, but this proved not to be the case. However, inhibition of cytoplasmic cap methylation resulted in a shift of upstream polyadenylation sites to annotated 3’ ends. Together, these results solidify cap homeostasis as a fundamental process of gene expression control and show cytoplasmic recapping can impact regulatory elements present at the ends of mRNA molecules.

References:
1) Trotman JB, Giltmier AJ, Mukherjee C, Schoenberg DR. RNA guanine-7 methyltransferase catalyzes the methylation of cytoplasmically recapped RNAs. Nucleic Acids Res. 2017;45:10726-10739.
2) Mukherjee C, Patil DP, Kennedy BA, Bakthavachalu B, Bundschuh R, Schoenberg DR. Identification of cytoplasmic capping targets reveals a role for cap homeostasis in translation and mRNA stability. Cell Rep. 2012;2:674-684.
3)Gentilella, Morón-Duran F, Fuentes P,eZweig-Rocha G, Riaño-Canalias F,Pelletier J, Ruiz M,Turón G, Castaño J, Tauler A, Bueno C, Menéndez P,Kozma SC, Thomas G. Autogenous Control of 5′TOP mRNA Stability by 40S Ribosomes. Molecular Cell 2017;67:55-70

Keywords: RNA, Cytoplasmic capping