Strong minor groove base conservation in sequence logos implies DNA distortion or base flipping during replication and transcription initiation

The sequence logo for DNA binding sites of the bacteriophage P1 replication protein RepA shows unusually high sequence conservation (similar to2 bits) at a minor groove that faces RepA. However, B-form DNA can support only 1 bit of sequence conservation via contacts into the minor groove. The high c onservation in RepA sites therefore implies a distorted DNA helix with dire ct or indirect contacts to the protein. Here I show that a high minor groov e conservation signature also appears in sequence logos of sites for other replication origin binding proteins (Rts1, DnaA, P4 alpha, EBNA1, ORC) and promoter binding proteins (sigma (70), sigma (D) factors). This finding imp lies that DNA binding proteins generally use non-B-form DNA distortion such as base flipping to initiate replication and transcription.