Article

Human histone acetyltransferase 1 protein preferentially acetylates H4 histone molecules in H3.1-H4 over H3.3-H4.

Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Journal of Biological Chemistry (Impact Factor: 4.65). 02/2012; 287(9):6573-81. DOI: 10.1074/jbc.M111.312637
Source: PubMed

ABSTRACT In mammalian cells, canonical histone H3 (H3.1) and H3 variant (H3.3) differ by five amino acids and are assembled, along with histone H4, into nucleosomes via distinct nucleosome assembly pathways. H3.1-H4 molecules are assembled by histone chaperone CAF-1 in a replication-coupled process, whereas H3.3-H4 are assembled via HIRA in a replication-independent pathway. Newly synthesized histone H4 is acetylated at lysine 5 and 12 (H4K5,12) by histone acetyltransferase 1 (HAT1). However, it remains unclear whether HAT1 and H4K5,12ac differentially regulate these two nucleosome assembly processes. Here, we show that HAT1 binds and acetylates H4 in H3.1-H4 molecules preferentially over H4 in H3.3-H4. Depletion of Hat1, the catalytic subunit of HAT1 complex, results in reduced H3.1 occupancy at H3.1-enriched genes and reduced association of Importin 4 with H3.1, but not H3.3. Finally, depletion of Hat1 or CAF-1p150 leads to changes in expression of a H3.1-enriched gene. These results indicate that HAT1 differentially impacts nucleosome assembly of H3.1-H4 and H3.3-H4.

0 Bookmarks
 · 
68 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Histone deposition onto DNA assisted by specific chaperones serves to form chromatin basic unit and to package the genome within the cell nucleus. The resulting chromatin organization, often referred to as the epigenome, contributes to a unique transcriptional program that defines cell identity. Importantly, during cellular life, substantial alterations in chromatin structure can arise due to cell stress, including DNA damage, which not only challenges the integrity of the genome but also threatens the epigenome. Over the past years, considerable efforts have been made to decipher chromatin dynamics in response to genotoxic stress, and to assess how it impacts on both genome and epigenome stability. Here, we review recent advances in understanding the mechanisms of DNA damage-induced chromatin plasticity in mammalian cells. We focus specifically on the dynamics of histone H3 variants in response to UV irradiation and highlight the role of their dedicated chaperones in restoring both chromatin structure and function. Finally, we discuss how, beyond restoring chromatin integrity, the cellular networks that signal and repair DNA damage may also provide a window of opportunity for modulating the information conveyed by chromatin.This article is protected by copyright. All rights reserved.
    FEBS Journal 03/2014; · 4.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: How the eukaryotic cell specifies distinct chromatin domains is a central problem in molecular biology. The ciliate protozoan Tetrahymena thermophila features a separation of structurally and functionally distinct germ-line and somatic chromatin into two distinct nuclei, the micronucleus (MIC) and macronucleus (MAC) respectively. To address questions about how distinct chromatin states are assembled in the MAC and MIC, we have initiated studies to define protein-protein interactions for T. thermophila chromatin-related proteins. Affinity purification followed by mass spectrometry analysis of the conserved Asf1 histone chaperone in T. thermophila revealed that it forms a complex with an importin β, ImpB6. Furthermore, these proteins co-localized to both the MAC and MIC in growth and development. We suggest that newly synthesized histones H3 and H4 in T. thermophila are transported via Asf1-ImpB6 in an evolutionarily conserved pathway to both nuclei where they then enter nucleus-specific chromatin assembly pathways. These studies set the stage for further use of functional proteomics to elucidate details of the characterization and functional analysis of the unique chromatin domains in T. thermophila. Asf1 is an evolutionarily conserved histone H3 and H4 histone chaperone that functions in replication dependent and independent chromatin assembly. Although Asf1 has been well studied in human and yeast (members of the Opisthokonta lineage of eukaryotes), questions remain concerning its mechanism of function. To obtain additional insight into Asf1 function we have initiated proteomic analysis in the ciliate protozoan T. thermophila, a member of the Alveolata lineage of Eukayotes. Our results suggest that an evolutionarily conserved function of Asf1 is mediating nuclear transport of newly synthesized histone H3 and H4.
    Journal of proteomics 10/2013; · 5.07 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The primary structure of Histone Acetyltransferase 1 (Hat1) has been conserved throughout evolution; however, despite its ubiquity, its cellular function is not well characterized. To study its in vivo acetylation pattern and function, we utilized shRNAmir against Hat1 expressed in the well-substantiated HeLa (human cervical cancer) cell line. To reduce the interference by enzymes with similar HAT specificity, we used HeLa cells expressing histone acetyltransferase Tip60 with mutated acetyl-CoA binding site that abrogates its enzyme activity (mutant HeLa-tip60). Two shRNAmir were identified that reduced the expression of the cytoplasmic and nuclear forms of Hat1. Cytosolic protein preparations from these two clones showed decreased levels of acetylation of lysine 5 (K5) and K12 on histone H4, with the concomitant loss of the acetylation of histone H2A at K5. This pattern of decreased acetylation of H2AK5 was well defined in preparations of histone protein and insoluble nuclear-protein (INP) fractions as well. Abrogating the Hat1 expression caused a 74 % decrease in colony-forming efficiency of mutant HeLa-tip60 cells, reduced the size of the colonies by 50 %, and decreased the amounts of proteins with molecular weights below 35 kDa in the INP fractions.
    Molecular and Cellular Biochemistry 03/2014; · 2.33 Impact Factor