IDENTIFICATION OF THE REGION IN YEAST S-II THAT DEFINES SPECIES-SPECIFICITY IN ITS INTERACTION WITH RNA-POLYMERASE-II

Yeast S-II was found to stimulate yeast RNA polymerase II only and not mouse RNA polymerase II, To identify the molecular region of S-II tha t defines species specificity, we constructed six hybrid S-II molecule s consisting of three regions from yeast: and/or Ehrlich cell S-II and examined their activity in terms of RNA polymerase II specificity and suppression of 6-azauracil. sensitivity in the yeast S-II null mutant . We found that the region 132-270 (amino acid positions) of yeast S-I I is indispensable for specific interaction with yeast RNA polymerase II in vitro and for suppression of 6-azauracil sensitivity in vivo. Th e corresponding region of Ehrlich cell S-II, the region 132-262, was a lso shown to be essential for its interaction with mouse RNA polymeras e II. This region is known to be less conserved than the Nand C-termin al regions in the S-II family suggesting that it is important in the i nteraction with transcription machinery proteins in a tissue and/or sp ecies-specific manner.