Alternative Linker Histone Permits Fast Paced Nuclear Divisions in Early Drosophila Embryo

In most animals, the start of embryogenesis requires specific histones. In Drosophila linker histone variant BigH1 is present in early embryos. To uncover the specific role of this alternative linker histone at early embryogenesis, we established fly lines in which domains of BigH1 have been replaced partially or completely with that of H1. Analysis of the resulting Drosophila lines revealed that at normal temperature somatic H1 can substitute the alternative linker histone, but at low temperature the globular and C-terminal domains of BigH1 are essential for embryogenesis. In the presence of BigH1 nucleosome stability increases and core histone incorporation into nucleosomes is more rapid, while nucleosome spacing is unchanged. Chromatin formation in the presence of BigH1 permits the fast-paced nuclear divisions of the early embryo. We propose a model which explains how this specific linker histone ensures the rapid nucleosome reassembly required during quick replication cycles at the start of embryogenesis

Heterogeneous photocatalysis of imidacloprid the effect of reaction parameters

The heterogeneous photocatalytic transformation of a harmful neonicotinoide insecticide, imidacloprid using TiO2 photocatalyst was the aim of the present work. The optimal TiO2 concentrations in oxygenated, aerated and oxygen-free suspensions were determined. However the dissolved oxygen enhanced the transformation rate of imidacloprid that was occurred in oxygen-free suspensions too. This can be explained by the relative high reactivity of imidacloprid towards hydrated electron, thus the relative contribution of direct charge can be significant. The effect of different additives was investigated to prove this assumption: NaF, methanol, t-butanol, chloroform, EDTA and KI. The pH and ionic strength of the solution have also significant effect, most likely by modifying the surface properties of TiO2. The results showed, that beside HO• based reaction the direct charge transfer must have significant role in the transformation of imidaclopride

Despite its sequence identity with canonical H4, Drosophila H4r product is enriched at specific chromatin regions

Histone variants are different from their canonical counterparts in structure and are encoded by solitary genes with unique regulation to fulfill tissue or differentiation specific functions. A single H4 variant gene (His4r or H4r) that is located outside of the histone cluster and gives rise to a polyA tailed messenger RNA via replication-independent expression is preserved in Drosophila strains despite that its protein product is identical with canonical H4. In order to reveal information on the possible role of this alternative H4 we epitope tagged endogenous H4r and studied its spatial and temporal expression, and revealed its genome-wide localization to chromatin at the nucleosomal level. RNA and immunohistochemistry analysis of H4r expressed under its cognate regulation indicate expression of the gene throughout zygotic and larval development and presence of the protein product is evident already in the pronuclei of fertilized eggs. In the developing nervous system a slight disequibrium in H4r distribution is observable, cholinergic neurons are the most abundant among H4r-expressing cells. ChIP-seq experiments revealed H4r association with regulatory regions of genes involved in cellular stress response. The data presented here indicate that H4r has a variant histone function

Magyar Tanítóképző 8 (1893) 04-05

Magyar Tanítóképző A Tanítóképző-intézeti Tanárok Országos Egyesületének közlönye 8. évfolyam, 4-5. füzet Budapest, 1893. április-május h