PMID:26970775

Citation	Sanvisens, N, Romero, AM, Zhang, C, Wu, X, An, X, Huang, M and Puig, S (2016) Yeast Dun1 Kinase Regulates Ribonucleotide Reductase Small Subunit Localization in Response to Iron Deficiency. J. Biol. Chem. 291:9807-17
Abstract	Ribonucleotide reductase (RNR) is an essential iron-dependent enzyme that catalyzes deoxyribonucleotide synthesis in eukaryotes. Living organisms have developed multiple strategies to tightly modulate RNR function to avoid inadequate or unbalanced deoxyribonucleotide pools that cause DNA damage and genome instability. Yeast cells activate RNR in response to genotoxic stress and iron deficiency by facilitating redistribution of its small heterodimeric subunit Rnr2-Rnr4 from the nucleus to the cytoplasm, where it forms an active holoenzyme with large Rnr1 subunit. Dif1 protein inhibits RNR by promoting nuclear import of Rnr2-Rnr4. Upon DNA damage, Dif1 phosphorylation by the Dun1 checkpoint kinase and its subsequent degradation enhances RNR function. In this report, we demonstrate that Dun1 kinase triggers Rnr2-Rnr4 redistribution to the cytoplasm in response to iron deficiency. We show that Rnr2-Rnr4 relocalization by low iron requires Dun1 kinase activity and phosphorylation site Thr-380 in the Dun1 activation loop, but not the Dun1 forkhead-associated domain. By using different Dif1 mutant proteins, we uncover that Dun1 phosphorylates Dif1 Ser-104 and Thr-105 residues upon iron scarcity. We observe that the Dif1 phosphorylation pattern differs depending on the stimuli, which suggests different Dun1 activating pathways. Importantly, the Dif1-S104A/T105A mutant exhibits defects in nucleus-to-cytoplasm redistribution of Rnr2-Rnr4 by iron limitation. Taken together, these results reveal that, in response to iron starvation, Dun1 kinase phosphorylates Dif1 to stimulate Rnr2-Rnr4 relocalization to the cytoplasm and promote RNR function.
Links	PubMed PMC4850316 Online version:10.1074/jbc.M116.720862
Keywords	Cell Cycle Proteins/genetics; Cell Cycle Proteins/metabolism; DNA Damage; Iron/metabolism; Protein Transport/physiology; Protein-Serine-Threonine Kinases/genetics; Protein-Serine-Threonine Kinases/metabolism; Ribonucleoside Diphosphate Reductase/genetics; Ribonucleoside Diphosphate Reductase/metabolism; Ribonucleotide Reductases/genetics; Ribonucleotide Reductases/metabolism; Saccharomyces cerevisiae/genetics; Saccharomyces cerevisiae/metabolism; Saccharomyces cerevisiae Proteins/genetics; Saccharomyces cerevisiae Proteins/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
YEAST:DUN1	involved_in	GO:0018107: peptidyl-threonine phosphorylation	ECO:0000315: mutant phenotype evidence used in manual assertion		P	has_direct_input:(UniProtKB:O13577) part_of:(GO:0010106)	Seeded From UniProt	complete
YEAST:DUN1	involved_in	GO:0018105: peptidyl-serine phosphorylation	ECO:0000315: mutant phenotype evidence used in manual assertion		P	has_direct_input:(UniProtKB:O13577) part_of:(GO:0010106)	Seeded From UniProt	complete

References

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