Bivalent histone modifications during tooth development

Histone methylation is one of the most widely studied post-transcriptional modifications. It is thought to be an important epigenetic event that is closely associated with cell fate determination and differentiation. To explore the spatiotemporal expression of histone H3 lysine 4trimethylation（H3K4me3） and histone H3 lysine 27 trimethylation（H3K27me3） epigenetic marks and methylation or demethylation transferases in tooth organ development, we measured the expression of SET7, EZH2, KDM5 B and JMJD3 via immunohistochemistry and quantitative polymerase chain reaction（qP CR） analysis in the first molar of BALB/c mice embryos at E13.5, E15.5, E17.5, P0 and P3, respectively. We also measured the expression of H3K4me3 and H3K27me3 with immunofluorescence staining. During murine tooth germ development, methylation or demethylation transferases were expressed in a spatial–temporal manner. The bivalent modification characterized by H3K4me3 and H3K27me3 can be found during the tooth germ development, as shown by immunofluorescence. The expression of SET7, EZH2 as methylation transferases and KDM5 B and JMJD3 as demethylation transferases indicated accordingly with the expression of H3K4me3 and H3K27me3 respectively to some extent. The bivalent histone may play a critical role in tooth organ development via the regulation of cell differentiation.

The Integrated Development of Weapon Technology and Weather Modification Technology

The advanced weather modification equipment was introduced,which was produced by China North Industries Corp（ NORINCO）. The advice of ordnance technology and weather modification technology integrated development was presented from aspects of system planning,overall design,market development and field extension. The feasibility and necessity of civil-military integrated development that the weapon technology could promote the development of civil product,i. e.,weather modification products,and as a result the civil technology＇s innovation could also accelerate the ordnance development was discussed.

Afteruse development of former landfll sites in Hong Kong

Landfll is one of the major methods in disposing of municipal solid waste(MSW) in Hong Kong. There are now 13 closed landfll sites in Hong Kong, and a restoration program has been launched since 1999 to transform the closed landfll sites back into recreational area. The MSW underneath these closed landfll sites will biodegrade slowly and gradually, releasing toxic gases and leachate. As there have only been a few afteruse development ever completed in Hong Kong, this paper describes the consideration in planning and design of two former landfll sites in Hong Kong–Ngau Chi Wan(NCW) and Jordan Valley(JV) landflls, in particular a discussion on the MSW settlement. Various models in predicting the longterm MSW settlement have been available. This paper reviews the applicability of these models to predict MSW settlement. However, as the predicted settlements can be signifcantly in error, they need sitespecifc calibration and validation. This paper therefore presents the settlement monitoring data in these former landfll sites over the last 30 years, and suggests modifying the Bjarngard and Edgers’ method for estimating this long-term settlement as well as the effect of additional surcharge due to afteruse development. Based on the regression of these data, compression indices Cce and C at different stages of the settlement in the modifed method have been calibrated and validated.

The Polycomb Complex PRC1:Composition and Function in Plants

Polycomb group（PcG） proteins are crucial epigenetic regulators conferring transcriptional memory to cell lineages.They assemble into multi-protein complexes,e.g.,Polycomb Repressive Complex 1 and 2（PRC1,PRC2）,which are thought to act in a sequential manner to stably maintain gene repression.PRC2 induces histone H3 lysine 27（H3K27） trimethylation（H3K27me3）,which is subsequently read by PRCl that further catalyzes H2A monoubiquitination（H2Aub1）,creating a transcriptional silent chromatin conformation.PRC2 components are conserved in plants and have been extensively characterized in Arabidopsis.In contrast,PRCl composition and function are more diverged between animals and plants.Only more recently,PRC1 existence in plants has been documented.Here we review the aspects of plant specific and conserved PRC1 and highlight critical roles of PRC1 components in seed embryonic trait determinacy,shoot stem cell fate determinacy,and flower development in Arabidopsis.

The micronuclear histone H3 clipping in the unicellular eukaryote Tetrahymena thermophila

Clipping of the histone H3 N-terminal tail has been implicated in multiple fundamental biological processes for a growing list of eukaryotes.H3 clipping,serving as an irreversible process to permanently remove some post-translational modifications(PTMs),may lead to noticeable changes in chromatin dynamics or gene expression.The eukaryotic model organism Tetrahymena thermophila is among the first few eukaryotes that exhibits H3 clipping activity,wherein the first six amino acids of H3 are cleaved off during vegetative growth.Clipping only occurs in the transcriptionally silent micronucleus of the binucleated T.thermophila,thus offering a unique opportunity to reveal the role of H3 clipping in epigenetic regulation.However,the physiological functions of the truncated H3 and its protease(s)for clipping remain elusive.Here,we review the major findings of H3 clipping in T.thermophila and highlight its association with histone modifications and cell cycle regulation.We also summarize the functions and mechanisms of H3 clipping in other eukaryotes,focusing on the high diversity in terms of protease families and cleavage sites.Finally,we predict several protease candidates in T.thermophila and provide insights for future studies.