Dense, systematic mutagenesis to identify the features required for CSEs

Investigate the sequence features required for CSE activity and selectivity. Overall design: Candidate region was synthesized as 80 190 nt oligonucleotides tiled in 5 nt steps. Each wild type 190 nt oligonucleotide was mirrored by a matching mutant in which the central 5 nt were deleted. The activity of mutant and mirrored wt oligos was compared to identify the import sequence.