Genome-Wide Distribution Polymerase II and Its Contr

specific to transcribed regions, suggesting that exclu-negatively regulated by chromatin structure. Such si-lencing or repression may be specific to a particular class of RNA polymerase or general to all three classes. Second, Pol I, Pol II, or Pol III can be actively recruited to a gene by distinct preinitiation complexes. Third, tran-scribing RNA polymerase can be removed from the sion of Pol II may require prior transcription by Pol II. Our results provide a high-resolution view of the global distribution of Pol II in yeast and expand the list of genes that are targets of Sen1-dependent termination. Furthermore, our findings suggest a general molecula