Protein-protein interactions with subunits of human nuclear RNase P

A yeast two-hybrid system was used to analyze interactions among the; prote in subunits of human nuclear RNase P themselves and with other interacting partners encoded in a HeLa cell cDNA library. Subunits hpop1,Rpp21, Rpp29, Rpp30, Rpp38, and Rpp40 are involved in extensive, but weak, protein-protei n interactions in the holoenzyme complex. Rpp14, Rpp20, and Rpp30 were foun d to have strong interactions with proteins encoded in the cDNA library. Th e small heat shock protein 27, which interacts with Rpp20 in the two-hybrid assay, binds to Rpp20 during affinity chromatography and can be found to b e associated with, and enhances the activity of, highly purified RNase P, R Nase P activity in HeLa cell nuclei also increases under the stress of heat shock.