title: Characterization of the human HSC20, an unusual DnaJ type III protein, involved in iron-sulfur cluster biogenesis.
abstract: The importance of mitochondrial iron-sulfur cluster (ISC) biogenesis for human health has been well established, but the roles of some components of this critical pathway still remain uncharacterized in mammals. Among them is human heat shock cognate protein 20 (hHSC20), the putative human homolog of the specialized DnaJ type co-chaperones, which are crucial for bacterial and fungal ISC assembly. Here, we show that the human HSC20 protein can complement for its counterpart in yeast, Jac1p, and interacts with its proposed human partners, hISCU and hHSPA9. hHSC20 is expressed in various human tissues and localizes mainly to the mitochondria in HeLa cells. However, small amounts were also detected extra-mitochondrially. RNA interference-mediated depletion of hHSC20 specifically reduced the activities of both mitochondrial and cytosolic ISC-containing enzymes. The recovery of inactivated ISC enzymes was markedly delayed after an oxidative insult of hHSC20-deficient cells. Conversely, overexpression of hHSC20 substantially protected cells from oxidative insults. These results imply that hHSC20 is an integral component of the human ISC biosynthetic machinery that is particularly important in the assembly of ISCs under conditions of oxidative stress. A cysteine-rich N-terminal domain, which clearly distinguishes hHSC20 from the specialized DnaJ type III proteins of fungi and most bacteria, was found to be important for the integrity and function of the human co-chaperone.
authors.affiliation: Molecular Medicine Program, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Helge
authors.initials: H
authors.lastname: Uhrigshardt
authors.forename: Anamika
authors.initials: A
authors.lastname: Singh
authors.forename: Gennadiy
authors.initials: G
authors.lastname: Kovtunovych
authors.forename: Manik
authors.initials: M
authors.lastname: Ghosh
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Rouault
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D049109:Cell Proliferation / Q000187:drug effects; D003545:Cysteine / Q000378:metabolism; D005816:Genetic Complementation Test; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010269:Paraquat / Q000633:toxicity; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013997:Time Factors
chemical_list: C490651:HSCB protein, human; D050956:HSP40 Heat-Shock Proteins; D007506:Iron-Sulfur Proteins; D018832:Molecular Chaperones; D003545:Cysteine; D010269:Paraquat