Journal Article

A HemK class glutamine-methyltransferase is involved in the termination of translation and essential for iron homeostasis in Arabidopsis

Yeh, Kuo-Chen, Kailasam, Sakthivel, Liu, Ming-Jung, Lin, Chih-Ching, Singh, Surjit

2020

Overview

• Iron (Fe) transport and utilization are controlled by Fe-dependent transcriptional cascades. Many genes participate in these processes, transcriptionally controlled by Fe-status. Thorough knowledge of the translational check-points is lacking. • We identified a non-response to Fe-deficiency1-1 (nrf1-1) mutant of Arabidopsis thaliana, which displayed a hypersensitive phenotype under Fe-deficient conditions. By mapping nrf1-1, we found that the AT3G13440 locus encoding a HemK methyltransferase is responsible for the phenotype. Analyses of ProUBQ10:NRF1CDS overexpression nrf1-1 lines and a T-DNA insertion mutant nrf1-2, confirmed that loss-of-function of NRF1 results in enhanced Fe-starvation-sensitivity. • NRF1 is required for the proper expression of the majority of Fe-deficiency-inducible (FDI) genes. The nrf1 mutants accumulated more polysomes in the roots, due to stalled ribosomes on several transcripts. Ribosome-footprint (RF) mapping revealed that ribosomes are stalled at a stop codon that amplified the stalling of trailing ribosomes. We detected higher RF levels in many FDI transcripts in nrf1-2. • Our study demonstrates the requirement of NRF1 for an accurate termination of protein synthesis essential not only for a precise iron homeostasis, but also cellular ion balance. NRF1 is also important for normal growth and development. A check-point that fine-tunes peptide release in plants is uncovered.

• Publisher: Wiley,Wiley Subscription Services, Inc
• Subject: Arabidopsis / Arabidopsis - enzymology / Arabidopsis - genetics / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / Deoxyribonucleic acid / DNA / Gene expression / Gene Expression Regulation, Plant / gene overexpression / Genes / Glutamine / growth and development / HemK methyltransferase / Homeostasis / ion homeostasis / Iron / Iron - metabolism / Iron deficiency / loci / loss-of-function mutation / Mapping / messenger RNA / Methyltransferase / Methyltransferases / Mutants / nutrient deficiencies / Peptide Chain Termination, Translational / peptide release / peptides / phenotype / Phenotypes / plant growth / Plant Roots - metabolism / Polyribosomes / Protein biosynthesis / Protein synthesis / ribosome stalling / Ribosomes / roots / Sensitivity enhancement / Stalling / Starvation / Stop codon / Transcription / transcription (genetics) / transfer DNA / translation / Translation termination