The transcription factors TFIID and SAGA are multi-subunit complexes involved in RNA polymerase II transcription. In the 8 June Nature Lee et al. use oligonucleotide arrays to analyze the relative requirement for the two complexes in yeast (Nature 2000, 405:701-704). Expression of about 70% of yeast genes requires one or more of the subunits shared between TFIID and SAGA, although individual subunits were required to varying extents, and no single subunit was required to the same extent as RNA polymerase II. The absence of single TFIID-specific and SAGA-specific subunits affects a distinct and generally small subset of genes. A minimum of about 30% of the genome is dependent on TFIID-specific subunits and around 12% of the genome on SAGA-specific subunits.