 Promoter bashing is often done with deletions from either the 5' or 3' end of the DNA strand; this assay is easier to perform based on repeated restriction digestion and gel-purifying fragments of specific sizes.It is often easiest to ligate the promoter into the reporter, generate a large amount of the reporter construct using PCR or growth in bacteria, and then perform serial restriction digests on this sample.The ability of upstream promoters can be easily assayed by removing segments from the 5' end, and the same for the 3' end of the strand for downstream promoters.