PUROMYCIN-SENSITIVE AMINOPEPTIDASE - SEQUENCE-ANALYSIS, EXPRESSION, AND FUNCTIONAL-CHARACTERIZATION

Among the molecular mechanisms that control the cell division cycle, p roteolysis has emerged as a key regulatory process enabling cells to p ass critical check points. Such proteolysis involves a cascade of enzy mes including a multisubunit complex termed 26S proteasome. Here we re port on the analysis of a novel mouse cDNA encoding the puromycin-sens itive aminopeptidase (PSA) and on its expression in COS cells and 3T3 fibroblasts. PSA is 27-40% homologous to several known Zn2+-binding am inopeptidases including aminopeptidase N. Immunohistochemical analysis revealed that PSA is localized to the cytoplasm and to the nucleus an d associates with microtubules of the spindle apparatus during mitosis . Furthermore, puromycin and bestatin both arrested the cell cycle, le ading to an accumulation of cells in G(2)/M phase, and ultimately indu ced cells to undergo apoptosis at concentrations that inhibit PSA. Con trol experiments including cycloheximide further suggested that the in duction of apoptosis by puromycin was not attributable to inhibition o f protein synthesis. Taken together, these data favor the novel idea t hat PSA participates in proteolytic events essential for cell growth a nd viability.