NuA4, an essential transcription adaptor/histone H4 acetyltransferase complex containing Esa1p and the ATM-related cofactor Tra1p

Post‐translational acetylation of histone H4 N‐terminal tail in chromatin has been associated with several nuclear processes including transcription. We report the purification and characterization of a native multisubunit complex (NuA4) from yeast that acetylates nucleosomal histone H4. NuA4 has an apparent molecular mass of 1.3 MDa. All four conserved lysines of histone H4 can be acetylated by NuA4. We have identified the catalytic subunit of the complex as the product of ESA1 , an essential gene required for cell cycle progression in yeast. Antibodies against Esa1p specifically immunoprecipitate NuA4 activity whereas the complex purified from a temperature‐sensitive esa1 mutant loses its acetyltransferase activity at the restrictive temperature. Additionally, we have identified another subunit of the complex as the product of TRA1 , an ATM‐related essential gene homologous to human TRRAP, an essential cofactor for c‐Myc‐ and E2F‐mediated oncogenic transformation. Finally, the ability of NuA4 to stimulate GAL4–VP16‐driven transcription from chromatin templates in vitro is also lost in the temperature‐sensitive esa1 mutant. The function of the essential Esa1 protein as the HAT subunit of NuA4 and the presence of Tra1p, a putative transcription activator‐interacting subunit, supports an essential link between nuclear H4 acetylation, transcriptional regulation and cell cycle control.