Recruitment of a 19S proteasome subcomplex to an activated promoter.

The 19S proteasome regulatory particle plays a critical role in cellular proteolysis. However, recent reports have demonstrated that 19S proteins play a nonproteolytic role in nucleotide excision repair and transcription elongation. We show by chromatin immunoprecipitation assays that proteins comprising the 19S complex are recruited to the GAL1-10 promoter by the Gal4 transactivator upon induction with galactose. This recruited complex does not contain proteins from the 20S proteolytic particle and includes a subset of the 19S proteins. This subset is also specifically retained from an extract by the Gal4 activation domain. These data indicate that in vivo, the base of the 19S complex functions independently of the larger complex and plays a direct, nonproteolytic role in RNA polymerase II transcription.