Pseudomonas aeruginosa infections can be virtually impossible to eradicate, and the evolution of resistance during antibiotic therapy is a significant concern. In this study, we use DNA microarrays to characterize the global transcriptional response of P. aeruginosa to clinical-like doses of the antibiotic ciprofloxacin and also to determine the component that is regulated by LexA cleavage and the SOS response. We find that genes involved in virtually every facet of metabolism are down-regulated in response to ciprofloxacin. The LexA-controlled SOS regulon identified by microarray analysis includes only 15 genes but does include several genes that encode proteins involved in recombination and replication, including two inducible polymerases known to play a role in mutation and the evolution of antibiotic resistance in other organisms. The data suggest that the inhibition of LexA cleavage during therapy might help combat this pathogen by decreasing its ability to adapt and evolve resistance.

Vaccinia virus is the prototypic orthopoxvirus and was the vaccine used to eradicate smallpox, yet the expression profiles of many of its genes remain unknown. Using a genome tiling array approach, we simultaneously measured the expression levels of all 223 annotated vaccinia virus genes during infection and determined their kinetics. Almost all of the genes were transcribed, and for 62 of these, this is the first empirical evidence of expression. Most remarkably, classification of the genes by their expression profiles revealed 35 genes exhibiting immediate‐early expression. Although a similar kinetic class has been described for other virus families, this is the first demonstration of its existence in orthopoxviruses. Despite expression levels higher than for genes in the other 3 kinetic classes, the functions of more than half of these remain unknown. Additionally, genes within each kinetic class were spatially grouped together in the genome. This genome‐wide picture of transcription alters our understanding of how orthopoxviruses regulate gene expression. This work was supported by National Institutes of Health grants ROI‐AI‐56268 and HHSN266200400124C.

We performed a randomized prospective trial comparing calcineurin inhibitor (CNI)-free to CNI-based imished prevalence of CAN and down-regulated expression of genes responsible for progression of CAN. All may provide for an alternative natural history with improved graft survival.

Schizosaccharomyces pombe Rad3 checkpoint kinase and its human ortholog ATR are essential for maintaining genome integrity in cells treated with genotoxins that damage DNA or arrest replication forks. Rad3 and ATR also function during unperturbed growth, although the events triggering their activation and their critical functions are largely unknown. Here, we use ChIP-on-chip analysis to map genomic loci decorated by phosphorylated histone H2A (γH2A), a Rad3 substrate that establishes a chromatin-based recruitment platform for Crb2 and Brc1 DNA repair/checkpoint proteins. Unexpectedly, γH2A marks a diverse array of genomic features during S-phase, including natural replication fork barriers and a fork breakage site, retrotransposons, heterochromatin in the centromeres and telomeres, and ribosomal RNA (rDNA) repeats. γH2A formation at the centromeres and telomeres is associated with heterochromatin establishment by Clr4 histone methyltransferase. We show that γH2A domains recruit Brc1, a factor involved in repair of damaged replication forks. Brc1 C-terminal BRCT domain binding to γH2A is crucial in the absence of Rqh1Sgs1, a RecQ DNA helicase required for rDNA maintenance whose human homologs are mutated in patients with Werner, Bloom, and Rothmund–Thomson syndromes that are characterized by cancer-predisposition or accelerated aging. We conclude that Rad3 phosphorylates histone H2A to mobilize Brc1 to critical genomic domains during S-phase, and this pathway functions in parallel with Rqh1 DNA helicase in maintaining genome integrity.

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