Cooperative interactions in transcriptional regulation.

Cooperative interactions between regulatory proteins and RNA polymerase are a common feature of transcriptional systems. We have developed a method, based on the electrophoresis mobility shift assay, for the measurement of cooperative effects in the binding of proteins to DNA restriction fragments. Using this approach we have identified a hitherto unknown interaction between the E. coli lactose repressor and CAP proteins. We suggest that this interaction plays a role in the control of the lactose operon that is not predicted by current regulatory models.