title: Protection of scaffold protein Isu from degradation by the Lon protease Pim1 as a component of Fe-S cluster biogenesis regulation.
abstract: Iron-sulfur (Fe-S) clusters, essential protein cofactors, are assembled on the mitochondrial scaffold protein Isu and then transferred to recipient proteins via a multistep process in which Isu interacts sequentially with multiple protein factors. This pathway is in part regulated posttranslationally by modulation of the degradation of Isu, whose abundance increases >10-fold upon perturbation of the biogenesis process. We tested a model in which direct interaction with protein partners protects Isu from degradation by the mitochondrial Lon-type protease. Using purified components, we demonstrated that Isu is indeed a substrate of the Lon-type protease and that it is protected from degradation by Nfs1, the sulfur donor for Fe-S cluster assembly, as well as by Jac1, the J-protein Hsp70 cochaperone that functions in cluster transfer from Isu. Nfs1 and Jac1 variants known to be defective in interaction with Isu were also defective in protecting Isu from degradation. Furthermore, overproduction of Jac1 protected Isu from degradation in vivo, as did Nfs1. Taken together, our results lead to a model of dynamic interplay between a protease and protein factors throughout the Fe-S cluster assembly and transfer process, leading to up-regulation of Isu levels under conditions when Fe-S cluster biogenesis does not meet cellular demands.
authors: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors: Szymon J
authors: SJ
authors: Ciesielski
authors: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706.
authors: Brenda
authors: B
authors: Schilke
authors: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706 Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk 80307, Poland.
authors: Jaroslaw
authors: J
authors: Marszalek
authors: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706 ecraig@wisc.edu.
authors: Elizabeth A
authors: EA
authors: Craig
mesh_terms: D049069:ATP-Dependent Proteases / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D059748:Proteolysis; D051573:Proto-Oncogene Proteins c-pim-1; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D013466:Sulfurtransferases / Q000378:metabolism
chemical_list: C121520:ISU1 protein, S cerevisiae; C115914:JAC1 protein, S cerevisiae; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; C496634:PIM1 protein, human; D051573:Proto-Oncogene Proteins c-pim-1; D013466:Sulfurtransferases; C115912:NFS1 protein, S cerevisiae; D049069:ATP-Dependent Proteases; C085155:PIM1 protein, S cerevisiae; D012697:Serine Endopeptidases