Promoter element sequences of the bovine U6, human U6-8 and mouse U6 promoters. The distal promoter regions containing the SPH and OCT sequences and proximal promoter regions containing the PSE and TATA sequence elements are shown for each promoter. Matches to the consensus sequence delineated at the top of the SPH, OCT and PSE sequences are shown in upper case (SPH consensus is from Schaub et al., 1999 , PSE consensus is from Dahlberg et al., 1988  and OCT consensus is from Sturm et al. 1988 ). Note that the relative positions of the SPH and OCT elements are switched in the mouse promoter.