ETS transcription factors are implicated in gene regulation during cell proliferation and in the development of the haematopoietic cell lineage. Characteristically, ETS proteins act in concert with other transcription factors and are regulated by post-translational modifications, most frequently phosphorylation. These events have been shown to modulate the DNA binding affinity and interactions of ETS transcription factors with co-activators, events that can ultimately determine the formation of productive transcription complexes on target gene promoters. However, direct implication of a transcription factor or one of its post-translational modifications in the regulation of a given gene requires detection of the modified factor at the target gene promoter. Chromatin immunoprecipitation assays were originally adopted to probe modifications to histone proteins associated with transcriptionally active genes in yeast. They have since been used to confirm the presence of numerous proteins at diverse gene promoters including, for example, recruitment of the mitogen-activated protein (MAP) kinases ERK1 and ERK2 to the promoters of mitogen-responsive genes. Here chromatin immunoprecipitation is used to demonstrate the inducible appearance of phosphorylated Elk-1 at the human c-fospromoter.
