Genomic binding sites of the yeast cell-cycle transcription factors SBF and MBF

Proteins interact with genomic DNA to bring the genome to life; and these i nteractions also define many functional features of the genome. SBF and MBF are sequence-specific transcription factors that activate gene expression during the G1/S transition of the cell cycle in yeast(1,2). SBF is a hetero dimer of Swi4 and Swi6, and MBF is a heterodimer of Mbp1 and Swi6 (refs 1, 3). The related Swi4 and Mbp1 proteins are the DNA-binding components of th e respective factors, and Swi6 may have a regulatory function(4,5). A small number of SBF and MBF target genes have been identified(3,6-10). Here we d efine the genomic binding sites of the SBF and MBF transcription factors in vivo, by using DNA microarrays. In addition to the previously characterize d targets, we have identified about 200 new putative targets. Our results s upport the hypothesis that SBF activated genes are predominantly involved i n budding, and in membrane and cell-wall biosynthesis, whereas DNA replicat ion and repair are the dominant functions among MBF activated genes(6,11). The functional specialization of these factors may provide a mechanism for independent regulation of distinct molecular processes that normally occur in synchrony during the mitotic cell cycle.