The Human Monocytic Leukemia Zinc Finger Histone Acetyltransferase Domain Contains DNA-binding Activity Implicated in Chromatin Targeting

Abstract

The human monocytic leukemia zinc finger (MOZ) protein is an essential transcriptional coactivator and histone acetyltransferase (HAT) that plays a primary role in the differentiation of erythroid and myeloid cells and is required to maintain hematopoietic stem cells. Chromosomal translocations involving the HAT-encoded region are also associated with acute myeloid leukemia. Here we present the x-ray crystal structure of the MOZ HAT domain and related biochemical studies. We find that the HAT domain contains a central region that is structurally and functionally conserved with the yeast MYST HAT protein Esa1, but contains more divergent N-and C-terminal regions harboring a TFIIIA-type zinc finger and helix-turn-helix DNA-binding motifs. Solution DNA-binding and acetyltransferase activity assays, in concert with mutagenesis, confirm that the MOZ HAT domain binds strongly to DNA through the zinc finger and helix-turn-helix motifs and that DNA binding and catalysis are not mutually exclusive. Consistent with the DNA-binding properties of MOZ, we also show that MOZ is able to acetylate nucleosomes and free histones equally well, whereas other HATs prefer free histones. Our results reveal, for the first time, that enzymatic and DNA-targeting activities can be contained within the same chromatin regulatory domain.The eukaryotic genome is packaged into chromatin, the highly organized DNA⅐protein complex that not only serves as a structural element in preserving genetic information but also as a dynamic scaffold from which nuclear processes occur such as transcription, replication, DNA repair, mitosis, and apoptosis (1, 2). The fundamental unit of chromatin is the nucleosome, consisting of 145-147 bp of DNA wrapped around an octameric histone core containing two molecules each of histone proteins H2A, H2B, H3, and H4. There are at least four types of protein domains that regulate DNA processes through chromatin modification. These include (a) enzymatic domains that either use ATP to translocate the DNA relative to the histone core proteins (3) or post-translationally modify the histone proteins (4, 5) and (b) non-enzymatic domains that recognize chromatin, either through interactions with unmodified or modified N-terminal histone tails or the DNA, or histone chaperone proteins that deposit histones or replace variant histones into chromatin. Many chromatin regulatory proteins often contain both an enzymatic and chromatin recognition domain, although, to date, there have been no reports of a single domain harboring both activities.Chromatin recognition domains that target histones include bromodomains (6, 7), which recognize specific acetyllysine modifications, chromodomains (8, 9), and tudor (10) domains, which bind specific methyllysine modifications, 14-3-3 domains, which recognize phosphoserine modifications (11), and SANT domains (12), which recognize unmodified histones. The SLIDE (12) and SWIRM (13, 14) domains are chromatin recognition modules that can target the DNA within nucleosomes.Among the enzymes that medi...

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“…At the structural level, it is located right next to the catalytic center (see Fig. S2C in the supplemental material) (24,67), so this region has an important role in modulating acetyltransferase activation.…”

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