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RNA Polymerase III Output Is Functionally Linked to tRNA Dimethyl-G26 Modification
Aneeshkumar G Arimbasseri1, Nathan H Blewett1, James R Iben1
1Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America.
Plos Genetics
|January 1, 2016
Summary
Maf1 repressor deletion paradoxically reduces tRNA suppressor activity by decreasing N2,N2-dimethyl G26 modification efficiency, a finding conserved across yeasts and human cells.
Area of Science:
- Molecular Biology
- Gene Regulation
- RNA Biology
Background:
- RNA polymerase III (RNAP III) synthesizes all eukaryotic tRNAs and its dysregulation is linked to cancer.
- Maf1 is a repressor of RNAP III, integrating cellular demands.
- Maf1 deletion in yeast causes global RNAP III activation but paradoxically reduces tRNA suppressor activity (antisuppression).
Purpose of the Study:
- To elucidate the mechanism behind Maf1-deletion-induced antisuppression in fission yeast.
- To investigate the role of tRNA modifications in this phenomenon.
- To determine if this mechanism is conserved in other organisms.
Main Methods:
- Utilized tRNA-HydroSeq to analyze tRNA levels in maf1Δ fission yeast.
- Assessed N2,N2-dimethyl G26 (m(2)2G26) modification efficiency using various methods.
- Investigated the effect of Trm1 overexpression and RNAP III mutations, and rapamycin treatment.
Main Results:
- Maf1 deletion in S. pombe caused antisuppression without significant changes in relative tRNA levels.
- Decreased m(2)2G26 modification efficiency on specific tRNAs correlated with antisuppression.
- Trm1 overexpression reversed antisuppression; RNAP III mutations and rapamycin treatment mimicked or modulated the effects.
Conclusions:
- Maf1-deletion-induced antisuppression results from competition for the Trm1 methyltransferase, leading to m(2)2G26 hypomodification.
- This hypomodification reduces the activity of suppressor tRNAs, explaining the antisuppression phenotype.
- The regulatory link between tRNA synthesis, m(2)2G26 modification, and suppressor activity is conserved from yeast to human cells.
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