Purification of Saccharomyces cerevisiae RNase H(70) and identification ofthe corresponding gene

We purified Saccharomyces cerevisiae RNase H(70) to homogeneity, using an o ptimized chromatographic purification procedure, Renaturation gel assay ass igned RNase H activity to a 70 kDa polypeptide. Sequencing of tryptic pepti des identified the open reading frame YGR276c on chromosome VII of the S. c erevisiae genome as the corresponding gene, which encodes a putative polype ptide of molecular mass of 62 849. We therefore renamed this gene RNH70, Im munofluorescence microscopy using a RNH70-EGFP fusion construct indicates n uclear localization of RNase PT(70). Deletion of RNH70 from the yeast genom e did not result in any serious phenotype under the conditions tested. Homo logy searches revealed striking similarity with a number of eukaryotic prot eins and open reading frames, among them the chimpanzee GOR protein, a homo log of a human autoimmune antigen, found to elicit autoimmune response in p atients infected with hepatitis C virus. (C) 1999 Federation of European Bi ochemical Societies.