ABSTRACT
Hydroxymethyl-glutaryl-CoA-reductase (HMG-CoA-reductase), the key enzyme for cholesterol synthesis and essential for the synthesis of the precursor for p21ras farnesylation, was inhibited in neuroblastoma cells by lovastatin or L-ascorbic acid. Both compounds inhibited clonogenic colony formation of neuroblastoma cells in soft agar. However, while the addition of mevalonate, the product of HMG-CoA-reductase, circumvented the inhibition by lovastatin it had no reversing effect on the inhibition by L-ascorbic acid. The role of reactive oxygen compounds generated by the degradation of catecholamines, and the pro-oxidative effects of L-ascorbic acid are discussed as mechanisms of action of L-ascorbic acid.
Subject(s)
Antineoplastic Agents/pharmacology , Ascorbic Acid/pharmacology , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Lovastatin/pharmacology , Neuroblastoma/pathology , Cell Division/drug effects , Dose-Response Relationship, Drug , Humans , Hydroxymethylglutaryl CoA Reductases/metabolism , Mevalonic Acid/analogs & derivatives , Mevalonic Acid/pharmacology , Neuroblastoma/enzymology , Tumor Cells, Cultured , Tumor Stem Cell AssayABSTRACT
While cloning breakpoint sequences of a leukemia patient exhibiting a t(5; 14) translocation, we identified a pseudogenic variant of a novel multigene family in proximity to the breakpoint. Chromosomal in situ hybridization suggested that the gene family is clustered on human chromosome 5q33-q34. The gene family is evolutionarily conserved. Northern blot analysis of mouse tissues revealed low-level expression of a functional member of this gene family in almost all samples. Marked levels of transcripts were detected by in situ hybridization in the retina, the olfactory epithelium, the peripheral neuronal ganglia, and distinct areas of the gut. The predicted protein displays striking similarity to a hypothetical protein of Caenorhabditis elegans (R10E11.3.) and to two yeast deubiquitinating enzymes, Ubp9 and Ubp13, albeit to a lesser extent. We expressed the putative coding region of the human gene in Escherichia coli and demonstrated that it indeed bears deubiquitinating activity based on its ability to cleave ubiquitin from a ubiquitin-beta-galactosidase fusion protein. This new deubiquitinating enzyme has been named UBH1, for ubiquitin hydrolyzing enzyme 1.
