Description

• Deoxyribonuclease from beef pancreas, DNase I, was first crystallized by Kunitz
• It is an endonuclease which splits phosphodiester linkages, preferentially adjacent to a pyrimidine nucleotide yielding 5'-phosphate terminated polynucleotides with a free hydroxyl group on position 3'
• The average chain of limit digest is a tetranucleotide
• DNase I acts upon single chain DNA, and upon double-stranded DNA and chromatin
• In the latter case, although histones restrict susceptibility to nuclease action, over a period of time nearly all chromatin DNA is acted upon
• According to Mirsky and Silverman, this could result from the looseness of histone attachment to DNA
• They found that lysine-rich histones more effectively block DNase access to DNA than arginine-rich histones