Characterization of prosomes in human lymphocyte subpopulations and their presence as surface antigens.

Prosomes, also called "multicatalytic proteinase" (MCP) or "proteasomes," are a new type of ubiquitous RNP particle present in some archeobacteria and in all eukaryotic cells tested from yeast to human. They were discovered as subcomplexes of untranslated messenger-ribonucleoproteins (mRNP) and later found to have a MCP activity putatively involved in antigen processing. Being composed of variable sets of characteristic proteins and associating small RNAs (pRNA), families of individual "mosaic" prosome particles seem to characterize the differentiation type and physiological state of individual cells and tissues.