Chick‐Embryo DNA Polymerase γ

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Abstract
The level of DNA polymerase .gamma. as compared to DNA polymerases .alpha. and .beta. was determined in chick embryo by means of specific tests: the amount of .gamma.-polymerase in the 12 day old chick embryo reaches about 15% of the total polymerase activity. This enzyme is mainly localized in nuclei and mitochondria, where it represents the prevailing if not the unique DNA polymerase activity. The mitochondrial DNA polymerase .gamma. is likely to be associated with the internal membrane or the matrix of this organelle since it is not removed by digitonin treatment. The .gamma.-polymerases were purified from chick embryo nuclei and mitochondria 500-700 times by means of DEAE-cellulose, phosphocellulose and hydroxyapatite chromatographies. The purified mitochondrial DNA polymerase .gamma. is closely related to the homologous enzyme purified from the nuclei of the same cells. They cannot be distinguished on the basis of their sedimentation, catalytical properties and response to inhibitors or denaturating agents. The purified .gamma. enzymes are distinct from the chick embryo DNA polymerases .alpha. and .beta. and are not inhibited by antibodies prepared against the latter enzymes. The nuclear and mitochondrial .gamma.-polymerases do not respond to the oncogenic RNA virus DNA polymerase assay with natural mRNA.

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