title: m-Calpain requires DNA for activity on nuclear proteins at low calcium concentrations.
abstract: m-Calpain (calpain II, m-CANP), which normally requires millimolar Ca2+ for activity in vitro, was capable of proteolyzing a number of matrix proteins in isolated rat liver nuclei at Ca2+ concentrations as low as 3 microM (Mellgren, R. L. (1991) J. Biol. Chem. 266, 13920-13924). Treatment of nuclei with deoxyribonuclease I eliminated the activity of m-calpain at low Ca2+ concentrations, while ribonuclease A and phospholipase C had no effect. Addition of DNA to DNase-treated nuclei restored m-calpain activity at low Ca2+. RNA had little if any effect. Eukaryotic and prokaryotic DNA were equally effective, and synthetic polydeoxyribonucleotides were also activators. m-Calpain did not bind to a DNA-cellulose column in the presence of 200 microM Ca2+, and m-calpain preincubated in the presence of DNA and 200 microM Ca2+ was not activated at low Ca2+ concentrations following removal of the DNA. DNA did not alter the Ca2+ requirement for m-calpain-catalyzed cleavage of casein. These results demonstrate that the Ca2+ requirement for proteolysis of nuclear matrix proteins by m-calpain can be dramatically decreased in the presence of DNA. Activation did not seem to be a result of DNA binding directly to calpain but appeared to require interaction of DNA, calpain, and calpain substrates in the nuclear matrix.
authors.affiliation: Department of Pharmacology and Therapeutics, Medical College of Ohio, Toledo 43699.
authors.forename: R L
authors.initials: RL
authors.lastname: Mellgren
authors.forename: K
authors.initials: K
authors.lastname: Song
authors.forename: M T
authors.initials: MT
authors.lastname: Mericle
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002154:Calpain / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism*; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D004247:DNA / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology*; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
chemical_list: D004269:DNA, Bacterial; D009687:Nuclear Proteins; D004247:DNA; D002154:Calpain; D002118:Calcium