Xbp1 is a transcriptional repressor with homology to the DNA binding domains of two cell-cycle regulatory transcription factors, Swi4 and Mbp1. Target genes bound and regulated by Xbp1, have been identified using differential display (DD). Because little was known about the regulation or function of Xbp1, we identified genes that were underrepresented in RNAs purified from cells in which Xbp1 was ectopically expressed. Four target genes, including three cyclin genes, were identified by DD and then confirmed by binding studies and Northern analysis. The binding site for Xbp1, previously identified by site selection, was present in these target genes and is conserved phylogenetically.
