Identification of the DNA Binding Subunit of RNA Polymerase II from Ehrlich Ascites Tumor Cells1

The DNA binding subunits of RNA polymerase II from Ehrlich ascites tumor cells were investigated in the following three ways. (1) RNA polymerase II was dissociated in urea and the binding of the dissociated subunits to DNA was investigated. (2) The RNA polymerase II: DNA complex was dissociated progressively with various concentrations of urea, and the subunits firmly attached to DNA were investigated. (3) RNA polymerase II was dissociated into subunits in a SDS-polyacrylamide gel containing urea and blotted onto a nitrocellulose filter. The filter was then incubated with 32P-nick-translated DNA to identify the DNA binding subunits. These procedures all showed that the largest subunit a of RNA polymerase II had strong affinity to DNA. It was found that a portion of subunits b and c could be recovered in DNA fraction when analyzed by procedures (1) and (2), but no significant DNA binding activity was detected when analyzed by procedure (3), suggesting that these subunits have either a much weaker affinity toward DN