This investigation describes the isolation and purification of a deacetylase from trout testes (Salmo gairdnerii) and its initial characterization, the results of which are summarized as follows; - Histone deacetylase activity was demonstrated in the 230,000 x g supernatant fraction of trout testes by a new and sensitive assay. - The deacetylase was purified by salt precipitation, molecular seive chromatography and subsequent ion exchange chromatography. - Two major fractions of enzyme activity were demonstratable with their approximate molecular sizes estimated. - The specificity of the enzyme towards different histone fractions appeared to undergo dramatic changes, depending on prior treatments. - Preliminary results as these furnished some basis for speculation regarding (a) the possible significance of deacetylation not only as a histone modification process but also in the role of gene regulation and (b) the logical prediction as to the existence of enzyme species exhibiting varying substrate specificities to cope with the distinct classes of histones unmasked in trout testes. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

"Histone deacetylases (HDACs) have become one of the leading areas of research for cancer, neurodegenerative diseases, diabetes, obesity, and inflammation. Although HDACs are currently expressible in mammalian cultures and yeast, it is important to explore other cost effective options. Here it is shown that class I HDACs are expressible in insect cells. As well as expressing full length domains for class I HDACs, predicted active domains have also been expressed. This information can be utilized in many areas for future research including identifying unique sites to allow development of specific inhibitors for each HDAC, and developing a better understanding of the specific role of each HDAC. "

Thesis (Ph. D.)--Ohio State University, 2006. / Full text release at OhioLINK's ETD Center delayed at author's request

The reversible process of histone acetylation and deacetylation is an important mechanism of epigenetic regulation in the control of gene expression and chromatin structure. In general, histone acetylation is related to gene activation, whereas histone deacetylation is associated with transcriptional gene silencing and maintenance of heterochromatin. A large number of histone deacetylases (HDACs), the enzymes that catalyze the reaction of histone deacetylation, have been identified in plants and other eukaryotes, and they were found to play crucial roles in plant growth and development. In Arabidopsis thaliana, histone deacetylase 1 (AtHD1) is a homolog of Saccharomyces cerevisiae Rpd3 that is a global transcriptional regulator. Downregulation of AtHD1 in transgenic Arabidopsis results in histone hyperacetylation and induces a variety of phenotypic and developmental defects, suggesting that AtHD1 is also a global regulator of many physiological and developmental processes. To characterize the expression pattern and distribution of AtHD1 in cells, the subcellular location of AtHD1 was determined by monitoring the expression of an AtHD1-GFP fusion protein in a transient expression assay and in transgenic Arabidopsis.The results show that AtHD1 is localized in the nucleus and appears to be excluded from the nucleolus. The histone deacetylase activity of AtHD1 was studied in an in vitro assay using radiolabeled histone peptides as a substrate. Recombinant AtHD1 produced by bacteria demonstrated a moderate but significant HDAC activity, whereas that produced by the baculovirus expression system did not have activity. This suggests that AtHD1 may require other cofactors or association with other proteins, rather than post-translational modifications, in order to have full HDAC activity. To study the possible interactions of AtHD1 with other proteins, a recombinant AtHD1 protein with two units of c-myc epitope fused to its C-terminus was expressed in transgenic Arabidopsis. We attempted to isolate proteins interacting with AtHD1 by co-immunoprecipitation (Co-IP). However, in the first few trials of Co-IP, a lot of contaminating proteins were present in the eluent along with the recombinant AtHD1-cmyc protein. Improvements in the experimental conditions are required for further investigation.

Les déacétylases dhistones (HDACs) constituent une famille denzymes identifiées initialement comme régulatrices du niveau dacétylation des histones, un processus important contrôlant la transcription génique. Comme leur nom lindique, il a longtemps été considéré que les seuls substrats des HDACs étaient les histones. Néanmoins, il est à présent démontré quelles peuvent aussi avoir dautres substrats nucléaires ou cytoplasmiques dont plusieurs facteurs de transcription et suppresseurs de tumeurs. Il a été montré que linhibition de lactivité des HDACs par des inhibiteurs globaux tels la trichostatine A (TSA) ou le suberoylanilide hydroxamique acide (SAHA) inhibe la croissance tumorale dans plusieurs modèles animaux. Linhibition des HDACs pourrait influencer tant les cellules tumorales que la néovascularisation de la tumeur (angiogenèse). Au cours des précédentes années de notre doctorat, nous avons étudié lune des HDACs de classe I, HDAC8. Nous avons découvert que cette HDAC, principalement cytoplasmique, est spécifiquement exprimée par les cellules de phénotype musculaire lisse et sassocie avec lactine ? des muscles lisses (? SMA) (Expression of histone deacetylase 8, a class I histone deacetylase, is restricted to cells showing smooth muscle differentiation in normal human tissues. Waltregny D, De Leval L, Glenisson W, Ly Tran S, North BJ, Bellahcene A, Weidle U, Verdin E, Castronovo V. American Journal of Pathology, 2004 Aug;165(2):553-64. - Histone deacetylase HDAC8 associates with smooth muscle alpha-actin and is essential for smooth muscle cell contractility. Glenisson W, Waltregny D, Tran SL, North BJ, Verdin E, Colige A, Castronovo V. FASEB Journal, 2005 Jun;19(8):966-8. - Novel smooth muscle markers reveal abnormalities of the intestinal musculature in severe colorectal motility disorders. T. Weidel, G.J.J.M. van Eys, W. Glénisson, D. Waltregny, V. Castronovo, J.-M. Vanderwinden. Neurogastroenterology and motility, 2006, 18(7):526-38.). Nous avions suspecté que HDAC8 pourrait jouer un rôle important dans la biologie de la cellule musculaire, potentiellement via la déacétylation de protéines cytosquelettiques ou encore par régulation de la transcription de gènes impliqués dans la différenciation musculaire lisse. Ainsi afin détudier limpact potentiel de HDAC8 et dautres HDACs dans ce processus, nous avons utilisé une approche dARN interférence dans un modèle de différenciation myofibroblastique (un modèle de différenciation musculaire lisse senso stricto nétant pas disponible). Les myofibroblastes (MFs) sont des cellules qui présentent des caractéristiques morphologiques et biochimiques intermédiaires entre des fibroblastes et des cellules musculaires lisses. La différenciation myofibroblastique, processus par lequel les fibroblastes aquièrent ces caractéristiques, peut être induite in vitro par des cytokines tel le TGF?1 (Transforming Growth Factor beta 1) mais sa régulation est encore mal connue. Les myofibroblastes jouent un rôle dans de multiples processus physiologiques, comme dans la cicatrisation, ainsi que dans des conditions pathologiques, comme dans linflammation chronique et le cancer. Plus précisément, les MFs pourraient jouer un rôle important dans le remodelage du stroma autour dun cancer, ce qui favoriserait la progression de certaines tumeurs (dont celles du colon). De récentes études ont montré que la TSA empêche, dans des cultures de fibroblastes de rat, linduction par le TGF?1 de la fibrogenèse (synthèse de procollagène ?1(I) et ?1(III) et d?-SMA). Cette observation suggère limplication dHDACs dans la régulation de la différenciation myofibroblastique. Nous avons donc entrepris didentifier la/les HDAC(s) régulant(s) spécifiquement(s) la différenciation myofibroblastique dans une culture primaire de fibroblastes de peau humaine grace à lutilisation de petits ARN interférants (siRNA) permettant de diminuer spécifiquement labondance de huit HDACs (HDAC1 à 8) tant au niveau de leur transcript que de leur protéine. Nous avons trouvé de manière reproductible que linduction de l?-SMA par le TGF?1 est bloquée par la transfection de siRNA spécifiques dHDAC4. Afin détudier quels sont les autres aspects de la fibrogenèse qui sont régulés par HDAC4, ainsi que le rôle quHDAC4 pourrait jouer dans la régulation de la signalisation du TGF?1, nous avons étudié lexpression de trois inhibiteurs endogènes de la voie de signalisation du TGF?. De manière intéressante, la diminution dHDAC4 induite par les siRNA entraine une augmentation de lexpression de TGIF et de TGIF2 mais pas de Smad7. Dans létat actuel de nos connaissance, cette observation serait la première à indiquer que le niveau dexpression de TGIF et de TGIF2 puisse être régulé par une HDAC. (Histone deacetylase 4 is required for TGF?1-induced myofibroblastic differentiation, W. Glénisson, D. Waltregny, V. Castronovo, BBA Mol cell Research, 2007).

The reversible process of histone acetylation and deacetylation is an important mechanism of epigenetic regulation in the control of gene expression and chromatin structure. In general, histone acetylation is related to gene activation, whereas histone deacetylation is associated with transcriptional gene silencing and maintenance of heterochromatin. A large number of histone deacetylases (HDACs), the enzymes that catalyze the reaction of histone deacetylation, have been identified in plants and other eukaryotes, and they were found to play crucial roles in plant growth and development. In Arabidopsis thaliana, histone deacetylase 1 (AtHD1) is a homolog of Saccharomyces cerevisiae Rpd3 that is a global transcriptional regulator. Downregulation of AtHD1 in transgenic Arabidopsis results in histone hyperacetylation and induces a variety of phenotypic and developmental defects, suggesting that AtHD1 is also a global regulator of many physiological and developmental processes. To characterize the expression pattern and distribution of AtHD1 in cells, the subcellular location of AtHD1 was determined by monitoring the expression of an AtHD1-GFP fusion protein in a transient expression assay and in transgenic Arabidopsis.The results show that AtHD1 is localized in the nucleus and appears to be excluded from the nucleolus. The histone deacetylase activity of AtHD1 was studied in an in vitro assay using radiolabeled histone peptides as a substrate. Recombinant AtHD1 produced by bacteria demonstrated a moderate but significant HDAC activity, whereas that produced by the baculovirus expression system did not have activity. This suggests that AtHD1 may require other cofactors or association with other proteins, rather than post-translational modifications, in order to have full HDAC activity. To study the possible interactions of AtHD1 with other proteins, a recombinant AtHD1 protein with two units of c-myc epitope fused to its C-terminus was expressed in transgenic Arabidopsis. We attempted to isolate proteins interacting with AtHD1 by co-immunoprecipitation (Co-IP). However, in the first few trials of Co-IP, a lot of contaminating proteins were present in the eluent along with the recombinant AtHD1-cmyc protein. Improvements in the experimental conditions are required for further investigation.

Among mammalian histone deacetylases (HDACs) identified so far, HDAC6 is unique in that it possesses tandem deacetylase domains, as well as a carboxyl-terminal zinc finger motif implicated in ubiquitin binding. HDAC6 has also been demonstrated to deacetylate tubulin and thus potentially contribute to regulation of cell motility. Although HDAC6 has been reported to interact with a variety of nuclear factors, this enzyme is predominantly localized to the cytoplasm. / Here I show that the subcellular localization of human HDAC6 is governed by additional elements not present in orthologues of this protein from other species. Human HDAC6 contains a unique insertion of eight or ten repeats of a Ser/Glu-containing tetradecapeptide sequence, here termed the SE14-repeat domain, which is responsible for mediating the Leptomycin B-resistant cytoplasmic retention of human HDAC6. Human HDAC6 also contains a second functional leucine-rich nuclear export signal when compared to murine HDAC6, and a region near the amino terminus of human HDAC6 is capable of mediating nuclear import. / I have also identified a previously uncharacterized protein containing a ubiquitin-like domain, here termed Ubl90, as a novel binding partner for HDAC6. Interestingly, Ubl90 binds to the deacetylase domains of HDAC6, rather than to the carboxyl-terminal zinc finger motif previously implicated in ubiquitin association. Ubl90 also interacts with several class I HDACs (HDAC1, HDAC2 and HDAC8), although more weakly than with HDAC6. When Ubl90 is overexpressed, it leads to the redistribution of HDAC1 from a nuclear to a pancellular localization, although this does not affect HDAC1-dependent transcriptional repression in a transient transfection assay. Like HDAC6, Ubl90 is capable of repressing Runx2-mediated transcriptional activation, and, when overexpressed, it leads to cell cycle disturbances similar to those seen with HDAC6 overexpression. These results suggest that Ubl90 and HDAC6 interact functionally, as well as physically.

Thesis (M. Med. Sc.)--University of Hong Kong, 2008.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xix, 278 p.; also includes graphics (some col.) Includes bibliographical references (p. 256-278).

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: histone deacetylase. Includes bibliographical references (p.35-36).