Nuclear particles containing RNA polymerase III complexes associated with the junctional plaque protein plakophilin 2

Plakophilin 2, a member of the arm-repeat protein family, is a dual locatio n protein that occurs both in the cytoplasmic plaques of desmosomes as an a rchitectural component and in an extractable form in the nucleoplasm. Here we report the existence of two nuclear particles containing plakophilin 2 a nd the largest subunit of RNA polymerase (pol) III (RPC155), both of which colocalize and are coimmuno-selected with other pol III subunits and with t he transcription factor TFIIIB, We also show that plakophilin 2 is present in the pol III holoenzyme. but not the core complex, and that it binds spec ifically to RPC155 in vitro. We propose the existence of diverse nuclear pa rticles in which proteins known as plaque proteins of intercellular junctio ns are complexed with specific nuclear proteins.