PMC:2195774 / 7523-9375 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/2195774","sourcedb":"PMC","sourceid":"2195774","source_url":"http://www.ncbi.nlm.nih.gov/pmc/2195774","text":"The COOH Terminus of either Ydj1 or Sis1 Is Essential for Viability\nThe nonessentiality of the substrate-binding regions of Sis1 and Ydj1 in vivo contrasts with the proposed critical role of Hsp40s in binding denatured substrates before presentation of those substrates to Hsp70. Two possibilities come to mind. Either binding of unfolded protein substrates is not critical for Hsp40 function in the cytosol, or there is significant functional overlap between Sis1 and Ydj1, and either protein can carry out this function.\nTo test these ideas, we created a strain that contains chromosomal disruptions of both YDJ1 and SIS1. Using combinations of plasmids expressing mutant and wild-type YDJ1 and SIS1 genes, we tested the importance of the COOH-terminal regions of these Hsp40s while maintaining the J plus G/F regions required for interaction with Hsp70. We constructed an sis1 ydj1 strain that carries a wild-type copy of SIS1 on a plasmid harboring URA3 to allow viability. To test for the ability of introduced genes to allow cell growth, transformants were spotted onto plates containing 5-fluoroorotic acid (5-FOA) to select for cells having lost the URA3-based plasmid containing SIS1. As expected from previous results (Yan and Craig 1999), a strain carrying a combination of wild-type YDJ1 and sis1-121, encoding the J plus G/F regions, was viable (Fig. 1 B). Similarly, the combination of wild-type SIS1 plus ydj1-134, encoding the J plus G/F plus spacer regions, was viable (Johnson and Craig 2000). However, the combination of sis1-121 plus ydj1-134 did not support viability, even though the regions necessary for Hsp70 interaction were retained. These results indicate that the COOH-terminal substrate-binding region of either Ydj1 or Sis1 is required in vivo, suggesting that Ydj1 and Sis1 may perform overlapping functions in the cell.","divisions":[{"label":"Title","span":{"begin":0,"end":67}}],"tracks":[]}