Human CtIP promotes DNA end resection

In the S and G2 phases of the cell cycle, DNA double-strand breaks (DSBs) are processed into single-stranded DNA, triggering ATR-dependent checkpoint signalling and DSB repair by homologous recombination. Previous work has implicated the MRE11 complex in such DSB-processing events. Here, we show that the human CtIP (RBBP8) protein confers resistance to DSB-inducing agents and is recruited to DSBs exclusively in the S and G2 cell-cycle phases. Moreover, we reveal that CtIP is required for DSB resection, and thereby for recruitment of replication protein A (RPA) and the protein kinase ATR to DSBs, and for the ensuing ATR activation. Furthermore, we establish that CtIP physically and functionally interacts with the MRE11 complex, and that both CtIP and MRE11 are required for efficient homologous recombination. Finally, we reveal that CtIP has sequence homology with Sae2, which is involved in MRE11-dependent DSB processing in yeast. These findings establish evolutionarily conserved roles for CtIP-like proteins in controlling DSB resection, checkpoint signalling and homologous recombination.     

On the ultrastructure of mammalian tendon

Zusammenfassung Es wird gezeigt, dass die zwischen gekreuzten Nicols für die Rattenschwanzsehne nachgewiesenen periodischen Bänder von fibrillären Strukturelementen ebener Wellenform abstammen und deren Ausstreckung das beobachtete Dehnungsverhalten erklärt², das auch für andere Säugetiere zutrifft.     

Rapid prototyping of patterned functional nanostructures

Living systems exhibit form and function on multiple length scales and at multiple locations. In order to mimic such natural structures, it is necessary to develop efficient strategies for assembling hierarchical materials. Conventional photolithography, although ubiquitous in the fabrication of microelectronics and microelectromechanical systems, is impractical for defining feature sizes below 0.1 micrometres and poorly suited to pattern chemical functionality. Recently, so-called 'soft' lithographic approaches have been combined with surfactant and particulate templating procedures to create materials with multiple levels of structural order. But the materials thus formed have been limited primarily to oxides with no specific functionality, and the associated processing times have ranged from hours to days. Here, using a self-assembling 'ink' we combine silica-surfactant self-assembly with three rapid printing procedures--pen lithography, ink-jet printing, and dip-coating of patterned self-assembled monolayers--to form functional, hierarchically organized structures in seconds. The rapid-prototyping procedures we describe are simple, employ readily available equipment, and provide a link between computer-aided design and self-assembled nanostructures. We expect that the ability to form arbitrary functional designs on arbitrary surfaces will be of practical importance for directly writing sensor arrays and fluidic or photonic systems.     

Altered nucleotide sequences of a translocated c-myc gene in Burkitt lymphoma

The nucleotide sequence of a translocated c-myc gene in a Burkitt lymphoma reveals multiple base changes in the coding region. Twenty-five base changes, generating 16 codon alterations, were found in the first coding exon; no changes occur in the second coding exon. These changes are probably the result of somatic mutations that occurred during and after translocation, and may contribute to oncogenesis by allowing synthesis of an altered c-myc gene product.     

DNA sequence and expression of the B95-8 Epstein-Barr virus genome

The complete (172,282 base pairs) nucleotide sequence of the B95-8 strain of Epstein-Barr virus has been established using the dideoxynucleotide/M13 sequencing procedure. Many RNA polymerase II promoters have been mapped and the mRNAs from these promoters have been assigned to the latent or early/late productive virus cycles. Likely protein-coding regions have been identified and three of these have been shown to encode a ribonucleotide reductase, a DNA polymerase and two surface glycoproteins.     

An electrochemical and microstructural characterization of steel-mortar admixed with corrosion inhibitors

The present research brings new insights on the role of admixed corrosion inhibitors in the processes of cement hydration and rebar corrosion.The admixing of NaCl and the corrosion inhibitors in fresh mortar was found to alter the morphology and microstructure of the hardened mortar at the steel-mortar interfacial region.The admixing of the inhibitors increased the risk of carbonation of cement hydrates at the steel-mortar interfacial region,but partially displaced chloride ions. Chloride and the admixed in...     

Sperm storage induces an immunity cost in ants

Ant queens are among the most long-lived insects known. They mate early in adult life and maintain millions of viable sperm in their sperm storage organ until they die many years later. Because they never re-mate, the reproductive success of queens is ultimately sperm-limited, but it is not known what selective forces determine the upper limit to sperm storage. Here we show that sperm storage carries a significant cost of reduced immunity during colony founding. Newly mated queens of the leaf-cutting ant Atta colombica upregulate their immune response shortly after completing their nest burrow, probably as an adaptive response to a greater exposure to pathogens in the absence of grooming workers. However, the immune response nine days after colony founding is negatively correlated with the amount of sperm in the sperm storage organ, indicating that short-term survival is traded off against long-term reproductive success. The immune response was lower when more males contributed to the stored sperm, indicating that there might be an additional cost of mating or storing genetically different ejaculates.     

Isolation and partial characterization of ovine lactoferrin.

Ovine lactoferrin was isolated by ammonium sulfate precipitation and ion exchange chromatography. Comparative analyses were performed with the bovine protein. Differences in the amino acid compositions and the tertiary structure of the proteins were observed.     

Biochemical and immunological comparison of phenotypes of horse serum tranferrins

Résumé Différents phénotypes homozygotes des transferrines du sérum équin ont été comparés par analyses de leurs caractéristiques biochimiques et immunologiques. Les compositions en acides aminés des différents phénotypes sont très voisines; les différences immunologiques déterminées par la micro-fixation du complément sont plus prononcées.