Open AccessA Novel H2A/H4 Nucleosomal Histone Acetyltransferase in Tetrahymena thermophila
Author(s) -
Reiko Ohba,
David J. Steger,
James E. Brownell,
Craig A. Mizzen,
Richard G. Cook,
Jacques Côté,
Jerry L. Workman,
C. David Allis
Publication year - 1999
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.19.3.2061
Subject(s) - biology , tetrahymena , histone h4 , histone acetyltransferase , chromatin , protein subunit , histone , transcription (linguistics) , biochemistry , nucleosome , acetyltransferase , microbiology and biotechnology , acetylation , dna , gene , linguistics , philosophy
Recently, we reported the identification of a 55-kDa polypeptide (p55) fromTetrahymena macronuclei as a catalytic subunit of a transcription-associated histone acetyltransferase (HAT A). Extensive homology between p55 and Gcn5p, a component of the SAGA and ADA transcriptional coactivator complexes in budding yeast, suggests an immediate link between the regulation of chromatin structure and transcriptional output. Here we report the characterization of a second transcription-associated HAT activity fromTetrahymena macronuclei. This novel activity is distinct from complexes containing p55 and putative ciliate SAGA and ADA components and shares several characteristics with NuA4 (for nucleosomal H2A/H4), a 1.8-MDa, Gcn5p-independent HAT complex recently described in yeast. A key feature of both the NuA4 andTetrahymena activities is their acetylation site specificity for lysines 5, 8, 12, and 16 of H4 and lysines 5 and 9 of H2A in nucleosomal substrates, patterns that are distinct from those of known Gcn5p family members. Moreover, like NuA4, theTetrahymena activity is capable of activating transcription from nucleosomal templates in vitro in an acetyl coenzyme A-dependent fashion. Unlike NuA4, however, sucrose gradient analyses of the ciliate enzyme, following sequential denaturation and renaturation, estimate the molecular size of the catalytically active subunit to be ∼80 kDa, consistent with the notion that a single polypeptide or a stable subcomplex is sufficient for this H2A/H4 nucleosomal HAT activity. Together, these data document the importance of this novel HAT activity for transcriptional activation from chromatin templates and suggest that a second catalytic HAT subunit, in addition to p55/Gcn5p, is conserved between yeast andTetrahymena .