19S-Proteasome (19S-PSM)

The 19S proteasome regulatory particle plays a critical role in cellular proteolysis. 19S proteins play a nonproteolytic role in nucleotide excision repair and transcription elongation. 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. 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. The 19S particle in eukaryotes consists of 19 individual proteins and is divisible into two subassemblies, a 10-protein base that binds directly to the α ring of the 20S core particle, and a 9-protein lid where polyubiquitin is bound.