DNA-binding chromosomal non-histone proteins. Isolation, characterization, and tissue specifity.

A fractionation schedule is described which allows the isolation of a group of chromosomal non-histone proteins (NP) with affinity for DNA. In polyacrylamide gel electrophoresis these proteins isolated from rat liver are represented principally by a group of low molecular weight polypeptides. The NP fraction comprises about 2-4% of the total chromatin protein content in rat liver or Novikoff hepatoma. Experiments in vivo and in vitro revealed that the NP proteins do not incorporate significant amounts of 32P. Complexes of the chromosomal proteins NP with homologous DNA are immunologically tissue specific and the specificity can be transferred by reconstituting the NP proteins from one tissue to the residual chromatin from another.