Investigating the role of MARF1-like (MFL) endoribonuclease genes in Arabidopsis
Date
2021
Authors
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Publisher
University of Delaware
Abstract
RNA decay in eukaryotes is mainly carried out by exoribonucleases and endoribonucleases, but the latter have been underappreciated. In metazoan nonsense-mediated mRNA decay (NMD), the endoribonuclease SMG6 cleaves certain mRNAs, leaving the 5' and 3' fragments to be degraded by the exosome and XRN1, respectively. Though SMG6 orthologs are absent in plants, recent studies in Arabidopsis thaliana indicate that some NMD transcripts are cleaved by an unknown endoribonuclease, and their 3' fragments over-accumulate in the absence of XRN4 (the plant cytosolic homolog of XRN1). Metazoan MARF1 is an endoribonuclease in humans and mice that cleaves targeted mRNAs via its catalytic NYN domain. Arabidopsis has several different NYN domain-containing proteins that we predicted to be homologs of metazoan MARF1. Importantly, one of these proteins (AtMFL1) localizes to P-bodies and has an RNA-dependent association with critical NMD factor AtUPF1. I therefore hypothesized that MARF1-like (MFL) endoribonucleases play a role in post-transcriptional control of gene expression in plants. ☐ The major goal of this project was to study the role of selected MFL endoribonucleases in Arabidopsis, particularly AtMFL1. Here I report the organ-specific expression of the AtMFL genes- AtMFL1 and AtMFL2 are ubiquitously expressed in all major organs, while AtMFL3 is minimally expressed in certain organs. I also report the subcellular localization of the AtMFL proteins- AtMFL1 localizes to cytosolic foci, AtMFL2 localizes to the cytosol and cytoskeleton, and AtMFL3 localizes to the nuclear membrane and cytosolic aggregates. Additionally, I report that AtMFL1-like proteins with catalytically active NYN domains are evolutionarily℗ conserved across many plant species. Finally, I provide evidence for the role of AtMFL1 as a cytosolic endoribonuclease that is involved in mRNA degradation.
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Keywords
Endoribonucleases, RNA decay, Arabidopsis thaliana, NMD transcripts