Size of native and denatured DNA of Ehrlich ascites tumour cells isolated in the presence of different protease concentrations
Schroeter, D.; Werner, D.; Meinzer, P.
European Journal of Cell Biology 24(1): 131-138
1981
ISSN/ISBN: 0171-9335 PMID: 7016543 Document Number: 170742
Native DNA molecules from mouse Ehrlich ascites tumor cells isolated either in the presence of 50 .mu.g/ml of proteinase K (PK-DNA) or in the presence of 6 mg/ml of autodigested pronase (PRO-DNA) are about equal in size. Since shear forces were avoided as much as possible during the isolation procedure, the largest molecules found were longer than 100 .mu.m. The average length of the traced molecules was 34.2 .mu.m for PK-DNA and 29.7 .mu.m for PRO-DNA. The length of PRO-DNA molecules undergoes a dramatic change during denaturation. The average contour length of denatured PRO-DNA molecules is 6.9 .mu.m. This reduction in length cannot be explained by shrinkage due to changes in ionic strength, pH and the effect of denaturing agents. PK-DNA identically denatured was not dramatically changed in size. PRO-DNA apparently contains more internal ends than PK-DNA. PRO-DNA is evidently much more sensitive to nuclease S1 than PK-DNA. Chromosomal DNA apparently is nicked or gapped in a protease-catalyzed reaction at distinct protease-sensitive sites.