Trichostatin A extends the lifespan of Drosophila melanogaster by elevating hsp22 expression

Aging can be defined as time-dependent, gradual anddetrimental changes in the structure and physiologicalfunction of an organism, ultimately leading to death [1].Factors influencing the aging process would change thelongevity. In Drosophila melanogaster, …     

Histone deacetylase inhibitors decrease reelin promoter methylation in vitro

We investigated the effects of agents that induce reelin mRNA expression in vitro on the methylation status of the human reelin promoter in neural progenitor cells (NT2). NT2 cells were treated with the histone deacetylase inhibitors, trichostatin A (TSA) and valproic acid (VPA), and the methylation inhibitor aza-2'-deoxycytidine (AZA) for various times. All three drugs reduced the methylation profile of the reelin promoter relative to untreated cells. The acetylation status of histones H3 and H4 increased following treatment with VPA and TSA at times as short as 15 min following treatment; a result consistent with the reported mode of action of these drugs. Chromatin immunoprecipitation experiments showed that these changes were accompanied by changes occurring at the level of the reelin promoter as well. Interestingly, AZA decreased reelin promoter methylation without concomittantly increasing histone acetylation. In fact, after prolonged treatments with AZA, the acetylation status of histones H3 and H4 decreased relative to untreated cells. We also observed a trend towards reduced methylated H3 after 18 h treatment with TSA and VPA. Our data indicate that while TSA and VPA act to increase histone acetylation and reduce promoter methylation, AZA acts only to decrease the amount of reelin promoter methylation.     

Regulated hyperacetylation of core histones during mouse spermatogenesis: involvement of histone deacetylases

Here we report a detailed analysis of waves of histone acetylation that occurs throughout spermatogenesis in mouse. Our data showed that spermatogonia and preleptotene spermatocytes contained acetylated core histones H2A, H2B and H4, whereas no acetylated histones were observed throughout meiosis in leptotene or pachytene spermatocytes. Histones remained unacetylated in most round spermatids. Acetylated forms of H2A and H2B, H3 and H4 reappeared in step 9 to 11 elongating spermatids, and disappeared later in condensing spermatids. The spatial distribution pattern of acetylated H4 within the spermatids nuclei, analyzed in 3D by immunofluorescence combined with confocal microscopy, showed a spatial sequence of events tightly associated with chromatin condensation. In order to gain an insight into mechanisms controlling histone hyperacetylation during spermiogenesis, we treated spermatogenic cells with a histone deacetylase inhibitor, trichostatin A (TSA), which showed a spectacular increase of histone acetylation in round spermatids. This observation suggests that deacetylases are responsible for maintaining a deacetylated state of histones in these cells. TSA treatment could not induce histone acetylation in condensing spermatids, suggesting that acetylated core histones are replaced by transition proteins without being previously deacetylated. Moreover, our data showed a dramatic decrease in histone deacetylases in condensing spermatids. Therefore, the regulation of histone deacetylase activity/concentration appears to play a major role in controling histone hyperacetylation and probably histone replacement during spermiogenesis.