Here the authors show that TFIIH interacts with the histone acetyl transferase KAT2A and recruits the ATAC/hSAGA complexes to chromatin; and that loss of xeroderma pigmentosum group B (XPB) function results in chromatin decondensation and increased gene expression through activation of KAT2A. The gene discussed is GTF2H5; the disease is xeroderma pigmentosum.