ELP3: Elp3, a yeast A-type HAT, appears to have a direct role in transcription in that it is part of the RNA polymerase II holoenzyme and is involved in transcriptional elongation. In S. cerevisiae, the three-subunit elongator complex binds tightly to RNA polymerase II and its hyperphosphorylated C-terminal repeat domain (CTD), participating in an elongation-competent form of holoenzyme. Elp3, the smallest elongator subunit, was identified by peptide mass spectrometry and found to have GNAT homology. Because of its GNAT homology, recombinant Elp3 was produced from insect cells and tested for HAT activity in in-gel assays. Under these conditions, Elp3 was able to acetylate all four core histones when presented with them individually (1)

Reference
1. Sterner, D.E.&Berger, S.L.Acetylation of histones and transcription-related factors. Microbiol. Mol. Biol. Rev.2000;64(2):435-459. PMID: 10839822.

    GCN5: The members of Gcn5-related N-acetyltransferase (GNAT) family structurally resemble the archetypal HAT Gcn5 and have been relatively well studied. They share the highly conserved catalytic HAT domain with characteristic sequence motifs, of which motif A notably binds acetyl-coA. Some members additionally have an N-terminal PCAF homology domain for substrate selectivity and a C-terminal bromodomain for binding acetylated lysine residues. As is the case with most HATs, GCN5 functions as the catalytic component in multi-subunit complexes SAGA, ADA and SLIK, playing important roles in transcriptional activation and various chromatin activities (1)

Reference
1. Jeon J. H., Lee Y. H.Histone acetylation in fungal pathogens of plants. Plant Pathol.J.2014;30(1):1-9. PMID: 25288980.

    HAT1: The best-understood set of acetyltransferases is the GNAT (Gcn5-related N-acetyltransferase) superfamily, which have been grouped together on the basis of their similarity in several homology regions and acetylation-related motifs. This group includes the HAT Gcn5, its close relatives, and at least three more distantly related HATs, Hat1, Elp3, and Hpa2. (1)

    Hat1 is the sole known example of a type B histone acetyltransferase. While it has long been presumed that type B histone acetyltransferases participate in the acetylation of newly synthesized histones during the process of chromatin assembly.

Reference
1. Sterner, D.E. & Berger, S.L.Acetylation of histones and transcription-related factors. Microbiol. Mol. Biol. Rev.2000;64(2):435-459. PMID: 10839822.

    HPA2: Hpa2 is a member of the Gcn5-related N-acetyltransferase (GNAT) superfamily, a family of enzymes with diverse substrates including histones, other proteins, arylalkylamines and aminoglycosides.As a GNAT superfamily member, this yeast protein was tested in vitro and found to acetylate histones H3 and H4, with a preference for lysine-14 of H3. Hpa2 has a high degree of homology with another yeast GNAT protein, Hpa3, which displayed very poor HAT activity in in vitro assays but did autoacetylate. (1)

Reference
1. Angus-Hill M. L., Dutnall R. N., Tafrov S. T., Sternglanz R. & Ramakrishnan V.Crystal structure of the histone acetyltransferase Hpa2: A tetrameric member of the Gcn5-related N-acetyltransferase superfamily. J Mol Biol294.1311-1325 (1999). PMID: 10600387.

    MYST: The MYST family, which was named after the initials of the founding members: MOZ, Ybf2/Sas3, Sas2, and Tip60, is the largest family of acetyltransferases with diverse biological functions. In the budding yeast, Esa1 of the NuA4 complex is known to be an essential HAT required for DNA repair and cell cycle progression. In animal systems, the role of MYST family HATs in stem cells, development and cancer have been thoroughly documented. It is of note that MYST family HAT complexes are known to have the broadest range of substrates including non-histone targets. The regulatory role and the ubiquity of protein acetylation had long been suspected to be comparable that of phosphorylation. (1)

Reference
1. Jeon J. H., Lee Y. H.Histone acetylation in fungal pathogens of plants. Plant Pathol.J.2014;30(1):1-9. PMID: 25288980.