RAD26, THE YEAST HOMOLOG OF HUMAN COCKAYNES-SYNDROME GROUP-B GENE, ENCODES A DNA-DEPENDENT ATPASE

Cells from Cockayne's syndrome (CS) patients are sensitive to ultravio let light and defective in preferential repair of the transcribed DNA strand, CS patients suffer from complex clinical symptoms, including s evere growth retardation, neurological degeneration, mental retardatio n, and cachexia, Two CS complementation groups, CSA and CSB, have been identified so far, RAD26 encodes the yeast counterpart of the CSB gen e, Here, we purify Rad26 protein to near homogeneity from yeast cells and show that it is a DNA-dependent ATPase, In contrast to the Mfd pro tein that functions in transcription-coupled repair in Escherichia col i, and which is a weak and DNA independent ATPase, Rad26 is a much mor e active ATPase, with a strict dependence on DNA. The possible role of Rad26 ATPase in the displacement of stalled RNA polymerase II from th e site of the DNA lesion and in the subsequent recruitment of a DNA re pair component is discussed.