DNA-dependent RNA polymerase A (or I) was purified from murine myeloma MOPC 21 by diethylaminoethyl Sephadex chromatography. Further separation from DNA polymerases, protein kinase, and DNA endonuclease was accomplished by polyriboadenylate-Sepharose affinity chromatography followed by gradient centrifugation. Yields following chromatography were 100%, but following gradient centrifugation only 25 to 30% of the activity remained. Addition of low-molecular-weight components increased yields to 50 to 60%. Several species of myeloma polymerase A could be detected, and subunits of 190,000 and 125,000 daltons were identified. No evidence of phosphorylation of the polymerase was found.


These studies were supported in part by USPHS Grants CA 13600, GM 13543, and GM 00100.

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