Homeostatic regulation of meiotic DSB formation by ATM/ATR.

Ataxia-telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed.

Significant changes in dietary intake and supplement use after breast cancer diagnosis in a UK multicentre study.

The diagnosis of cancer can motivate survivors to alter their lifestyle habits. Healthcare providers need to be aware of what changes patients are likely to make in order to derive more pertinent recommendations; however, few studies have reported pre- and post-diagnostic lifestyle behaviours. Semi-quantitative food frequency questionnaires (FFQs) completed approximately 1 year after diagnosis were used to evaluate dietary intake and supplement use before and after diagnosis in a cohort of 1,560 breast cancer patients participating in the UK, prospective DietCompLyf study. Intake of fruit and vegetables, wholegrains and lean sources of protein increased significantly post-diagnosis (P < 0.05, each). Conversely, after diagnosis consumption of high-fat, high-sugar products, red meat, coffee, some alcoholic drinks and refined grains significantly decreased (P < 0.05, each). Post-diagnostic changes in diet were accompanied by changes in the intake of macronutrients and a number of vitamins and minerals. Supplement use was highly prevalent (56.1%) pre-diagnosis, increasing to 62.8% after diagnosis (P = 0.001). Fish oils, multivitamin and minerals, and evening primrose oil were most often used and the proportion of users significantly increased (P < 0.05, each) after diagnosis. The percentage of women using oestrogenic botanical supplements (OBSs) was small but more than doubled to 8.4% after diagnosis (P < 0.05). British women participating in the DietCompLyf study reported significant changes in dietary intake and supplement use after their breast cancer diagnosis. These findings contribute to our understanding of female cancer survivors' dietary behaviours which is crucial for developing and implementing recommendations.

Improved strains and plasmid vectors for conditional overexpression of His-tagged proteins in Haloferax volcanii.

Research into archaea will not achieve its full potential until systems are in place to carry out genetics and biochemistry in the same species. Haloferax volcanii is widely regarded as the best-equipped organism for archaeal genetics, but the development of tools for the expression and purification of H. volcanii proteins has been neglected. We have developed a series of plasmid vectors and host strains for conditional overexpression of halophilic proteins in H. volcanii. The plasmids feature the tryptophan-inducible p.tnaA promoter and a 6xHis tag for protein purification by metal affinity chromatography. Purification is facilitated by host strains, where pitA is replaced by the ortholog from Natronomonas pharaonis. The latter lacks the histidine-rich linker region found in H. volcanii PitA and does not copurify with His-tagged recombinant proteins. We also deleted the mrr restriction endonuclease gene, thereby allowing direct transformation without the need to passage DNA through an Escherichia coli dam mutant.

RadB acts in homologous recombination in the archaeon Haloferax volcanii, consistent with a role as recombination mediator.

Homologous recombination plays a central role in the repair of double-strand DNA breaks, the restart of stalled replication forks and the generation of genetic diversity. Regulation of recombination is essential since defects can lead to genome instability and chromosomal rearrangements. Strand exchange is a key step of recombination - it is catalysed by RecA in bacteria, Rad51/Dmc1 in eukaryotes and RadA in archaea. RadB, a paralogue of RadA, is present in many archaeal species. RadB has previously been proposed to function as a recombination mediator, assisting in RadA-mediated strand exchange. In this study, we use the archaeon Haloferax volcanii to provide evidence to support this hypothesis. We show that RadB is required for efficient recombination and survival following treatment with DNA-damaging agents, and we identify two point mutations in radA that suppress the ΔradB phenotype. Analysis of these point mutations leads us to propose that the role of RadB is to act as a recombination mediator, which it does by inducing a conformational change in RadA and thereby promoting its polymerisation on DNA.