N4 RNA polymerase II sites of transcription initiation

The RNA polymerase responsible for the synthesis of coliphage N4 middle RNAs, N4 RNA polymerase II, is composed of two subunits of 30,000 and 40,000 molecular weight. It is the smallest DNA-dependent RNA polymerase characterized to date. We have determined the sequences surrounding the sites of in vivo transcription initiation for this enzyme. Two regions of sequence homology are present: a box at +1, 3' AAAT 5', and a box, 3' TTCTGGAC 5' at a variable distance (16 to 24 base-pairs) upstream from +1. Possible mechanisms for recognition of these sequences are discussed.