An estimated two billion persons are latently infected with Mycobacterium tuberculosis . The host factors that initiate and maintain this latent state and the mechanisms by which M. tuberculosis survives within latent lesions are compelling but unanswered questions. One such host factor may be nitric oxide (NO), a product of activated macrophages that exhibits antimycobacterial properties. Evidence for the possible significance of NO comes from murine models of tuberculosis showing progressive infection in animals unable to produce the inducible isoform of NO synthase and in animals treated with a NO synthase inhibitor. Here, we show that O 2 and low, nontoxic concentrations of NO competitively modulate the expression of a 48-gene regulon, which is expressed in vivo and prepares bacilli for survival during long periods of in vitro dormancy. NO was found to reversibly inhibit aerobic respiration and growth. A heme-containing enzyme, possibly the terminal oxidase in the respiratory pathway, likely senses and integrates NO and O 2 levels and signals the regulon. These data lead to a model postulating that, within granulomas, inhibition of respiration by NO production and O 2 limitation constrains M. tuberculosis replication rates in persons with latent tuberculosis.

SummaryBackground Poly(ADP-ribose) polymerase (PARP) inhibitors have activity in ovarian carcinomas with homologous recombination defi ciency. Along with BRCA1 and BRCA2 (BRCA) mutations genomic loss of heterozygosity (LOH) might also represent homologous recombination defi ciency. In ARIEL2, we assessed the ability of tumour genomic LOH, quantifi ed with a next-generation sequencing assay, to predict response to rucaparib, an oral PARP inhibitor.

SummaryUnlike many pathogens that are overtly harmful to their hosts, Mycobacterium tuberculosis can persist for years within humans in a clinically latent state. Latency is often linked to hypoxic conditions within the host. Among M. tuberculosis genes induced by hypoxia is a putative transcription factor, Rv3133c/ DosR. We performed targeted disruption of this locus followed by transcriptome analysis of wild-type and mutant bacilli. Nearly all the genes powerfully regulated by hypoxia require Rv3133c/DosR for their induction. Computer analysis identified a consensus motif, a variant of which is located upstream of nearly all M. tuberculosis genes rapidly induced by hypoxia. Further, Rv3133c/DosR binds to the two copies of this motif upstream of the hypoxic response gene alphacrystallin. Mutations within the binding sites abolish both Rv3133c/DosR binding as well as hypoxic induction of a downstream reporter gene. Also, mutation experiments with Rv3133c/DosR confirmed sequence-based predictions that the C-terminus is responsible for DNA binding and that the aspartate at position 54 is essential for function. Together, these results demonstrate that Rv3133c/DosR is a transcription factor of the two-component response regulator class, and that it is the primary mediator of a hypoxic signal within M. tuberculosis .

Purpose Hallmarks of germline BRCA1/2-associated ovarian carcinomas include chemosensitivity and improved survival. The therapeutic impact of somatic BRCA1/2 mutations and mutations in other homologous recombination (HR) DNA repair genes is uncertain. Experimental Design Using targeted capture and massively parallel genomic sequencing, we assessed 390 ovarian carcinomas for germline and somatic loss-of-function mutations in 30 genes, including BRCA1, BRCA2, and 11 other genes in the HR pathway. Results 31% of ovarian carcinomas had a deleterious germline (24%) and/or somatic (9%) mutation in one or more of the 13 HR genes: BRCA1, BRCA2, ATM, BARD1, BRIP1, CHEK1, CHEK2, FAM175A, MRE11A, NBN, PALB2, RAD51C, and RAD51D. Non-serous ovarian carcinomas had similar rates of HR mutations to serous carcinomas (28% vs. 31%, p=0.6), including clear cell, endometrioid, and carcinosarcoma. The presence of germline and somatic HR mutations was highly predictive of primary platinum sensitivity (p=0.0002) and improved overall survival (p=0.0006), with median overall survival 66 months in germline HR mutation carriers, 59 months in cases with a somatic HR mutation, and 41 months for cases without an HR mutation. Conclusions Germline or somatic mutations in HR genes are present in almost one-third of ovarian carcinomas, including both serous and non-serous histologies. Somatic BRCA1/2 mutations and mutations in other HR genes have a similar positive impact on overall survival and platinum responsiveness as germline BRCA1/2 mutations. The similar rate of HR mutations in non-serous carcinomas supports their inclusion in PARP inhibitor clinical trials.