ABSTRACT
BCL-2 family proteins regulate the mitochondrial apoptotic pathway. BOK, a multidomain BCL-2 family protein, is generally believed to be an adaptor protein similar to BAK and BAX, regulating the mitochondrial permeability transition during apoptosis. Here we report that BOK is a positive regulator of a key enzyme involved in uridine biosynthesis; namely, uridine monophosphate synthetase (UMPS). Our data suggest that BOK expression enhances UMPS activity, cell proliferation, and chemosensitivity. Genetic deletion of Bok results in chemoresistance to 5-fluorouracil (5-FU) in different cell lines and in mice. Conversely, cancer cells and primary tissues that acquire resistance to 5-FU down-regulate BOK expression. Furthermore, we also provide evidence for a role for BOK in nucleotide metabolism and cell cycle regulation. Our results have implications in developing BOK as a biomarker for 5-FU resistance and have the potential for the development of BOK-mimetics for sensitizing 5-FU-resistant cancers.
Subject(s)
Proto-Oncogene Proteins c-bcl-2/metabolism , Uridine/metabolism , Animals , Apoptosis/drug effects , Biomarkers, Tumor/metabolism , Cell Proliferation/drug effects , DNA Damage , Drug Resistance, Neoplasm/drug effects , Fluorouracil/pharmacology , Mammals , Mice , Multienzyme Complexes/metabolism , Orotate Phosphoribosyltransferase/metabolism , Orotidine-5'-Phosphate Decarboxylase/metabolism , Protein Binding/drug effects , Protein Domains , Proto-Oncogene Proteins c-bcl-2/chemistry , Tumor Suppressor Protein p53/metabolismABSTRACT
Here, we review recent studies aimed at defining the importance of quaternary structure to a model oligomeric enzyme, dihydrodipicolinate synthase. This will illustrate the complementary and synergistic outcomes of coupling the techniques of analytical ultracentrifugation with enzyme kinetics, in vitro mutagenesis, macromolecular crystallography, small angle X-ray scattering, and molecular dynamics simulations, to demonstrate the role of subunit self-association in facilitating protein dynamics and enzyme function. This multitechnique approach has yielded new insights into the molecular evolution of protein quaternary structure.