The multifunctional protein p100 is a vital transcriptional regulator that increases gene transcription by forming a physical bridge between promoter-specific transcription factors and the basal transcription machinery. To identify potential signal transduction pathways in which human p100 acts as a coregulator and to find target promoter regions that may interact with p100, we performed a promoter microarray assay called chromatin immunoprecipitation-guided ligation and selection (ChIP-GLAS). From this assay, we determined that a set of promoter fragments, including several factors in the transforming growth factor beta (TGF-β) signaling pathway, exhibited interaction with p100. The ChIP-GLAS data were validated by RT-PCR assessing the mRNA expression of various factors in the TGF-β signaling pathway in cell lines.