DNAse sensitivity

DNase-sensitive fiber with dimensions compatible with that of a Watson-Crick double helix. 

Matthaei, J. H., Nirenberg, M. W. Characteristics and stabilization of DNAse-sensitive protein synthesis in E. coli extracts. Proc. nat. Acad. Sci. (Wash.) 47, 1580-1588 (1961). 

Vidali, G., Boffa, L.C., Bradbury, E.M., and Allfrey, V.G. (1978) Butyrate suppression of histone deacetylation leads to accumulation of multiacetylated forms of histones H3 and H4 and increased DNase I sensitivity of the associated DNA sequences. Proc. Natl. Acad. Sci. 75(5), 2239-2243. 

Wood, W.I. and Felsenfeld, G. (1982) Chromatin structure of the chicken beta-globin gene region. Sensitivity to DNase I, micrococcal nuclease, and DNase II. J. Biol. Chem. 10 257(13), 7730-7736. 

Any electromechanical device that utilizes an automated feedback servomotor to regulate the addition of titrant (a standardized solution of acid or base within a syringe) into a reaction vessel or sample to maintain pH. The rate at which the syringe expels its contents allows one to determine the rate of a chemical reaction producing or consuming protons. There are many such enzyme-catalyzed reactions whose kinetics can be examined with a pH Stat. For maximal sensitivity, one must use weakly buffered solutions. In his classical kinetic investigation of DNA bond scission by DNase, Thomas measured the rate of base addition in a pH Stat. The number of bonds cleaved was linear with time, and this was indicative of random scission. 

The rate of hydrolysis of DNA, RNA, and polynucleotides can be measured by a sensitive spectrophotometric assay which is based on the hyperchromicity that occurs upon hydrolysis of these substrates (S). The enzyme has a 7-fold greater affinity for denatured DNA than for RNA (8). No inhibitory products accumulate during the course of the reaction. The pH optimum for RNase and DNase activities is between 9 and 10, depending on the Ca2+ concentration. At higher pH values less Ca2+ is required. The inhibitory effect of high Ca2+ observed consistently by many investigators is more pronounced at higher pH values (S). 

When acid DNase activity is assayed by the acid-solubility method the optimal DNA concentration is 0.4 mg/ml (9) and higher substrate concentrations appear to be inhibitory (16, 21, 34)- It has been shown, however, that this inhibition is because increasing substrate concentration decreases the efficiency of acid-soluble oligonucleotide release since the number of breaks per unit length of DNA is lower. If a direct method of estimating enzymic activity is used, such as the determination of phosphatase-sensitive phosphate, it can be shown that the inhibition by high substrate seen by the acid solubility method is only apparent (34)-... 

DNA are readily accessible to RNA polymerase binding and transcription. By contrast, most DNA in eukaryotic cells exists in a condensed form (chromatin), which is not readily accessible to transcription. The small fraction of DNA accessible to the RNA polymerase in any given cell type is especially sensitive to cleavage by mild treatment with bovine pancreatic DNase I. These regions of the DNA often contain bound RNA polymerase, modified histones, and additional nonhistone proteins. Active regions are often undermethylated compared with the total DNA. Most of the methylated groups in DNA are on the C residues in the CG sequence. 

---