CCAAT box revisited: bidirectionality, location and context

The so-called CCAAT box is believed to be a major promoter element of higher eukaryotes though it is ill-defined being deduced from very limited sequence data. The comprehensive computer analysis of an unbiased set of 168 promoters presented here removes several of the persisting uncertainties. In particular, it delineates the region of preferential occurrence of the CCAAT element to -110 to -50 relative to the initiation site, suggests that integrity of this pentamer is essential, and confirms bidirectionality as a general property of this element. Within the above region the signal is found to occur in a specific sequence context which is an important supplement to its description.