Histone acetylation in Zea mays.I. Activities of histone acetyltransferases and histone deacetylases

DEAE-Sepharose chromatography of extracts from Zea mays meristematic cells revealed multiple histone acetyltransferase and histone deacetylase enzyme forms. An improved method for nuclear isolation allowed us to discriminate nuclear and cytoplasmic enzymes. Two nuclear histone acetyltransferases, A1 and A2, a cytoplasmic B-enzyme and two nuclear histone deacetylases, HD1 and HD2, have been identified. The histone specificity of the different enzyme forms has been studied in an in vitro system, using chicken erythrocyte histones as substrate. The cytoplasmic histone acetyltransferase B is the predominant enzyme, which acetylates mainly histone H4 and to a lesser extent H2A. The nuclear histone acetyltransferase A1 preferentially acetylates H3 and also H4, whereas enzyme A2 is specific for H3. This substrate specificity was confirmed with homologous Z. mays histones. The two histone deacetylases differ from each other with respect to ionic strength dependence, inhibition by acetate and butyrate, and substrate specificity. The strong inhibitory effect of acetate on histone deacetylases was exploited to distinguish different histone acetyltransferase forms.     

Histone acetyltransferases and histone deacetylases of Physarum polycephalum

DEAE-Sepharose chromatography of plasmodial extracts of the myxomycete Physarum polycephalum reveals the presence of multiple histone acetyltransferases and histone deacetylases. Five putative histone acetyltransferases and histone deacetylases. Five putative histone acetyltransferase forms with different substrate specificity can be discriminated: one enzyme which acetylates all core histones and four enzymes with a preference for each of H3, H2A, H2B or H4. Two histone deacetylases, HD1 and HD2, can be discriminated. They differ with respect to substrate specificity and pH-dependence. The substrate specificity of histone deacetylases is determined using HPLC-purified individual core histone species. The order of acetylated substrate preference is H2A>>H3≥H4> H2B for HD1, H3>H2A>H4 for HD2, respectively; HD2 is inactive with H2B as substrate.     

Effects of histone acetylation on chromatin structure

The effect of histone acetylation was monitored on CHO chromatin structure, following the addition of 7 mM Na-butyrate to the cell culture medium. The properties of both control and hyperacetylated chromatins and nuclei were investigated by circular dichroism, ethidium bromide intercalation, differential scanning calorimetry, and affinity chromatography. Our results are compatible with modest but significant alterations in the various levels of chromatin organization, as a result of the charge neutralization of some lysine residues within the N-terminal region of the histonic octamer. Namely, large statistically significant differences do exist in the heat capacity thermograms of native nuclei, where unfolding into single nucleofilament of the highly packed native chromatin superfiber appears associated with acetylation; at the same time CD, EB, and affinity chromatography point to modest but consistent differences in the compactness of isolated nucleosomes and polynucleosomes. J. Cell. Biochem. 64:466–475. © 1997 Wiley-Liss, Inc.     

Deletion of host histone acetyltransferases and deacetylases strongly affects Agrobacterium-mediated transformation of Saccharomyces cerevisiae

Agrobacterium tumefaciens is a plant pathogen that genetically transforms plant cells by transferring a part of its Ti-plasmid, the T-strand, to the host cell. Under laboratory conditions, it can also transform cells from many different nonplant organisms, including the yeast Saccharomyces cerevisiae . Collections of S. cerevisiae strains have been developed with systematic deletion of all coding sequences. Here, we used these collections to identify genes involved in the Agrobacterium -mediated transformation (AMT) of S. cerevisiae . We found that deletion of genes ( GCN5 , NGG1 , YAF9 and EAF7 ) encoding subunits of the SAGA, SLIK, ADA and NuA4 histone acetyltransferase complexes highly increased the efficiency of AMT, while deletion of genes ( HDA2 , HDA3 and HST4 ) encoding subunits of histone deacetylase complexes decreased AMT. These effects are specific for AMT as the efficiency of chemical (lithium acetate) transformation was not or only slightly affected by these deletions. Our data are consistent with a positive role of host histone deacetylation in AMT.     

RANKL induces NFATc1 acetylation and stability via histone acetyltransferases during osteoclast differentiation

The MTM (myotubularin)/MTMR (myotubularin-related) protein family is comprised of 15 lipid phosphatases, of which nine members are catalytically active. MTMs are known to play a fundamental role in human physiology as gene mutations can give rise to X-linked myotubular myopathy or Charcot-Marie-Tooth disease, which manifest in skeletal muscle or in peripheral neurons respectively. Interestingly, studies have shown MTMR2 and MTMR5, two MTM family members, to be highly expressed in the testis, particularly in Sertoli and germ cells, and knockout of either gene resulted in spermatogenic defects. Other studies have shown that MTMR2 functions in endocytosis and membrane trafficking. In the testis, MTMR2 interacts and co-localizes with c-Src/phospho-Src-(Tyr?1?), a non-receptor protein tyrosine kinase that regulates the phosphorylation state of proteins at the apical ES (ectoplasmic specialization), a unique type of cell junction found between Sertoli cells and elongating/elongated spermatids. In the present review, we highlight recent findings that have made a significant impact on our understanding of this protein family in normal cell function and in disease, with the emphasis on the role of MTMs and MTMRs in spermatogenesis. We also describe a working model to explain how MTMR2 interacts with other proteins such as c-Src, dynamin 2, EPS8 (growth factor receptor pathway substrate 8) and ARP2/3 (actin-related protein 2/3) at the apical ES and the apical TBC (tubulobulbar complex; tubular-like invaginations that function in the disassembly of the apical ES and in the recycling of its components) to regulate spermiation at late stage VIII of the seminiferous epithelial cycle.