Progressive Polycomb Assembly on H3K27me3 Compartments Generates Polycomb Bodies with Developmentally Regulated Motion

Polycomb group (PcG) proteins are conserved chromatin factors that maintain silencing of key developmental genes outside of their expression domains. Recent genome-wide analyses showed a Polycomb (PC) distribution with binding to discrete PcG response elements (PREs). Within the cell nucleus, PcG proteins localize in structures called PC bodies that contain PcG-silenced genes, and it has been recently shown that PREs form local and long-range spatial networks. Here, we studied the nuclear distribution of two PcG proteins, PC and Polyhomeotic (PH). Thanks to a combination of immunostaining, immuno-FISH, and live imaging of GFP fusion proteins, we could analyze the formation and the mobility of PC bodies during fly embryogenesis as well as compare their behavior to that of the condensed fraction of euchromatin. Immuno-FISH experiments show that PC bodies mainly correspond to 3D structural counterparts of the linear genomic domains identified in genome-wide studies. During early embryogenesis, PC and PH progressively accumulate within PC bodies, which form nuclear structures localized on distinct euchromatin domains containing histone H3 tri-methylated on K27. Time-lapse analysis indicates that two types of motion influence the displacement of PC bodies and chromatin domains containing H2Av-GFP. First, chromatin domains and PC bodies coordinately undergo long-range motions that may correspond to the movement of whole chromosome territories. Second, each PC body and chromatin domain has its own fast and highly constrained motion. In this motion regime, PC bodies move within volumes slightly larger than those of condensed chromatin domains. Moreover, both types of domains move within volumes much smaller than chromosome territories, strongly restricting their possibility of interaction with other nuclear structures. The fast motion of PC bodies and chromatin domains observed during early embryogenesis strongly decreases in late developmental stages, indicating a possible contribution of chromatin dynamics in the maintenance of stable gene silencing

Isolation, Characterization and X-ray Structure Determination of the Schiff Base Ligand: 5-Methyl-2-phenyl-4-[phenyl-(4-phenyl-thiazol-2-ylamino)- methylene]-2,4-dihydro-pyrazol-3-one

The structure of the amine tautomer of the new Schiff base derived from 4-benzoyl-5-methyl-2-phenyl-2,4-dihydro-pyrazol- 3-one (2) and 4-phenyl-thiazol-2-ylamine (3) was confirmed by means of single crystal X-ray diffraction. The title compound (4) was synthesized and crystals were grown from a mixture of dichloromethane and n-hexane (1:3). Single crystal X-ray diffraction analysis show that the structure is primarily stabilized by strong intramolecular N3–H3A···O1 hydrogen bonds [N3–H3A = 0.883(19) Å, H3A···O1=1.925(18) Å, N3···O1=2.6901(13) Å, with an angle for N3–H3A···O1=144.1(17) °] and this leads to the formation of a pseudo nine-membered hydrogen bonded pattern. Elemental analysis, FTIR andNMRanalyses have been employed to characterize the crystal.KEYWORDS Pyrazolone, thiazole, Schiff base, tautomer, X-ray structure.PDF and Supp files attache

Isolation, characterization and x-ray structure determination of the schiff base ligand: 5-methyl-2-phenyl-4-[phenyl-(4-phenyl-thiazol-2-ylamino)-methylene]-2,4-dihydro-pyrazol-3-one

The structure of the amine tautomer of the new Schiff base derived from 4-benzoyl-5-methyl-2-phenyl-2,4-dihydro-pyrazol-3-one (2) and 4-phenyl-thiazol-2-ylamine (3) was confirmed by means of single crystal X-ray diffraction. The title compound (4) was synthesized and crystals were grown from a mixture of dichloromethane and n-hexane (1:3). Single crystal X-ray diffraction analysis show that the structure is primarily stabilized by strong intramolecular N3-H3A-O1 hydrogen bonds [N3-H3A = 0.883(19) Ẳ, H3A-O1 = 1.925(18) Ẳ, N3-O1 = 2.6901(13) A, with an angle for N3-H3A-O1 = 144.1(17) °] and this leads to the formation of a pseudo nine-membered hydrogen bonded pattern. Elemental analysis, FTIR and NMR analyses have been employed to characterize the crystalNational Research Foundation (South Africa

Archaeological assessment reveals Earth’s early transformation through land use

Environmentally transformative human use of land accelerated with the emergence of agriculture, but the extent, trajectory, and implications of these early changes are not well understood. An empirical global assessment of land use from 10,000 years before the present (yr B.P.) to 1850 CE reveals a planet largely transformed by hunter-gatherers, farmers, and pastoralists by 3000 years ago, considerably earlier than the dates in the land-use reconstructions commonly used by Earth scientists. Synthesis of knowledge contributed by more than 250 archaeologists highlighted gaps in archaeological expertise and data quality, which peaked for 2000 yr B.P. and in traditionally studied and wealthier regions. Archaeological reconstruction of global land-use history illuminates the deep roots of Earth’s transformation and challenges the emerging Anthropocene paradigm that large-scale anthropogenic global environmental change is mostly a recent phenomenon

Mollusc harvesting in the Pre - European contact Pacific Islands: investigating resilience and sustainability

Mollusc shells, which are often quite numerous in archaeological sites throughout the Pacific Islands, offer good proxies for assessing environmental change as well as human impact. Documented changes in species size, richness, and abundance have often been interpreted as evidence of resource abuse by shellfish gatherers. While this may be valid in some cases, archaeologists need to consider other variables to explain change (or stability) in shell distribution. A better understanding of ecological and biological (life history) characteristics associated with shell midden deposits, as well as greater awareness of ethnographic and ethnoarchaeological data on the interaction between people and varieties of marine resources, may result in a reinterpretation of past human behavior. A growing interest in indigenous resource management among contemporary Pacific Island communities has led some archaeologists to seek tangible evidence of community resilience and sustainable use of resources in the past. This chapter draws primarily from direct observations and semi-structured interviews among mollusc gatherers in Kiribati, eastern Micronesia, and examines selected case studies of archaeological shell deposits from the Pacific Islands that could shed new light on marine resource management to complement the more widespread research conclusions that depict human impact in largely negative terms