ChIP-chip scatter plot of anti-hSET1 (A300-289A) enriched DNA binding sites versus input reference DNA. A. 10 ug of A300-289A was used to immunoprecipitate chromatin from K562 cells according to Ren et al (Genes Dev. 2002 16: 245-256). Immunoprecipitated DNA and reference DNA were amplified via ligation-mediated PCR and the products labeled with fluorescent dUTPs. The labeled ChIP and reference DNA were pooled, hybridized to a DNA microarray, and analyzed. Data points below the +3 SD curve (red line) represent significantly enriched binding sites. B. As a control, a similar experiment was performed using normal rabbit IgG. Compared to the anti-hSET1 ChIP, normal rabbit IgG showed little enrichment.