a, Expression profile of the MYC locus. The long and short RNA profile of HeLa cells on Affymetrix tiling arrays. Red rectangles indicate the designed synthetic PASRs (MYC_1–5 are denoted by numbers and sequence information is provided in Supplementary Table 2) corresponding to peaks in the sRNA array profile. b, MYC mRNA expression levels in HeLa cells as measured by quantitative PCR with reverse transcription (n = 3, P values <0.01). c, Effects of PASR transfections on a MYC-responsive luciferase transcriptional reporter in HeLa cells was measured as relative light units (RLU) (n = 2, *P <0.01, **P <0.001). For reference, a control 33-mer and an siRNA directed against luciferase (siGL3) are shown.