Heterochromatin protein 1 is recruited to various types of DNA damage

Heterochromatin protein 1 (HP1) family members are chromatin-associated proteins involved in transcription, replication, and chromatin organization. We show that HP1 isoforms HP1-α, HP1-β, and HP1-γ are recruited to ultraviolet (UV)-induced DNA damage and double-strand breaks (DSBs) in human cells. This response to DNA damage requires the chromo shadow domain of HP1 and is independent of H3K9 trimethylation and proteins that detect UV damage and DSBs. Loss of HP1 results in high sensitivity to UV light and ionizing radiation in the nematode Caenorhabditis elegans, indicating that HP1 proteins are essential components of DNA damage response (DDR) systems. Analysis of single and double HP1 mutants in nematodes suggests that HP1 homologues have both unique and overlapping functions in the DDR. Our results show that HP1 proteins are important for DNA repair and may function to reorganize chromatin in response to damage

Rekonstitution des Chromophors und der Funktion von Bakteriorhodopsin aus Halobacterium halobium

Ein Modell der lichtgetriebenen Protonenpumpe Bakteriorhodopsin postulierte die direkte Beteiligung der Wasserstoffe in der 4-Stellung des Cyclohexenringes des Retinalchromophors an dem Vorgang der Protonenverschiebung. Mittels Blockaden der Retroform-Bildung von Retinal durch chemische Modifizierungen des Cyclohexenringes (4-Hydroxy-Retinal, 5,6-Epoxy-Retinal) konnten nach Einbau der modifizierten Moleküle in die isolierte Purpurmembran und nach Zugabe zu Halobakterien mit unterdrückter Retinalsynthese die direkte Beteiligung des Cyclohexenringes an der Protonenpumpe mit großer Wahrscheinlichkeit ausgeschlossen werden

Cannabidiol revisited

The crystal structure of cannabidiol, C21H30O2, {systematic name: 2-[(1R,6R)-3-methyl-6-(prop-1-en-2-yl)cyclohex-2-enyl]-5-pentylbenzene-1,3-diol}, was determined earlier by Jones et al. [(1977). Acta Cryst. B33, 3211–3214] and Ottersen & Rosenqvist [(1977). Acta Chem. Scand. B31, 749–755]. In both investigations, the absolute configuration is given as R,R, referring to Mechoulam et al. [(1967.J. Am. Chem. Soc. 89, 4552–4554]. In the latter, the absolute configuration was identified by chemical means. Using the advantages of modern single-crystal X-ray diffractometers such as area detectors and high-intensity radiation sources, a high-quality structure determination including the absolute configuration was possible and is shown in this work. Furthermore, the rather uncommon Cu Kβ wavelength radiation was applied for the structure determination, which confirmed the absolute structure to be R,R

In vivo dynamics of chromatin-associated complex formation in mammalian nucleotide excision repair

Chromatin is the substrate for many processes in the cell nucleus, including transcription, replication, and various DNA repair systems, all of which require the formation of multiprotein machineries on the chromatin fiber. We have analyzed the kinetics of in vivo assembly of the protein complex that is responsible for nucleotide excision repair (NER) in mammalian cells. Assembly is initiated by UV irradiation of a small area of the cell nucleus, after which the accumulation of GFP-tagged NER proteins in the DNA-damaged area is measured, reflecting the establishment of the dual-incision complex. The dynamic behavior of two NER proteins, ERCC1-XPF and TFIIH, was studied in detail. Results show that the repair complex is assembled with a rate of ≈30 complexes per second and is not diffusion limited. Furthermore, we provide in vivo evidence that not only binding of TFIIH, but also its helicase activity, is required for the recruitment of ERCC1-XPF. These studies give quantitative insight into the de novo assembly of a chromatin-associated protein complex in living cells

Assembly of multiprotein complexes that control genome function

Live-cell imaging studies aided by mathematical modeling have provided unprecedented insight into assembly mechanisms of multiprotein complexes that control genome function. Such studies have unveiled emerging properties of chromatin-associated systems involved in DNA repair and transcription