NUCLEIC ACID-BINDING REGIONS OF THE 2ND-LARGEST SUBUNIT OF DROSOPHILARNA-POLYMERASE-II IDENTIFIED BY SOUTHWESTERN BLOTTING

Analysing overlapping bacterially expressed fragments of the second-la rgest subunit of Drosophila melanogaster RNA polymerase II in Southwes tern DNA binding assays we have identified regions that have the poten tial to bind nucleic acids non-specifically. A region exhibiting stron g DNA binding is located in the N-terminal part of the molecule (amino acids 357-504) and some weak DNA binding is observed for the C-termin al part (amino acids 860-1160). The non-specific DNA binding behavior of these regions is similar to that of the native enzyme. Most of the known mutations responsible for rifampicin resistance map to a region of the Escherichia coli beta subunit corresponding to the N-terminal n ucleic acid-binding region, indirectly supporting the notion that this region participates in interaction with the RNA transcript in ternary complexes.