Fig. 3.

cAMP stimulates Ser-133 phosphorylation uniformly over CREB-occupied genes. (a) Comparison of CREB occupancy and presence of CREs in human promoters. For each promoter category (those with predicted CRE, those without predicted CRE, and all genes), the distribution of confidence levels (P values) from ChIP-chip results is shown. Graph shows percentage of promoters within each category at specific P-value range. P values were computed from three independent CREB ChIP experiments with HEK293T cells. (b) Analysis of P-CREB levels over human promoters by ChIP-chip assay of HEK293T cells at 0, 1, and 4 h after exposure to FSK. Randomly selected subsets of ChIP-positive CREB target genes from cAMP responsive and nonresponsive genes were used to compare P-CREB profiles. (c) Western blot assay showing levels of total CREB and P-CREB in HEK293T cells after FSK treatment for times indicated.