Effects of cyclic GMP upon DNA binding by a calf thymus nuclear protein fraction

Abstract

Summary Proteins extracted from calf thymus nuclei with 2 M NaCl and separated by Bio-Rex 70 column chromatography were analyzed for their ability to bind to cyclic nucleotides and to calf thymus DNA. Several nuclear protein fractions contain both cyclic GMP-binding and DNA-binding activities. One protein fraction binds cyclic GMP with an apparent high affinity, as determined by equilibrium dialysis. At low concentrations (10 −6 M – 10 −9 M) cyclic GMP slightly enhances the ability of proteins in this fraction to bind 125 I-labelled DNA, while at concentrations >10 −5 M the cyclic nucleotide is strongly inhibitory to DNA binding.