The superoxide anion (O2−)-generating system is an important mechanism of innate immune response against microbial infection in phagocytes and is involved in signal transduction mediated by various physiological and pathological signals in phagocytes and other cells, including B lymphocytes. The O2−-generating system is composed of five specific proteins: p22-phox, gp91-phox, p40-phox, p47-phox, p67-phox, and a small G protein, Rac. Little is known regarding epigenetic regulation of the genes constituting the O2−-generating system. In this study, by analyzing the GCN5 (one of most important histone acetyltransferases)-deficient DT40 cell line, we show that GCN5 deficiency causes loss of the O2−-generating activity. Interestingly, transcription of the gp91-phox gene was drastically downregulated (to ∼4%) in GCN5-deficient cells. To further study the involvement of GCN5 in transcriptional regulation of gp91-phox, we used in vitro differentiation system of U937 cells. When human monoblastic U937 cells were cultured in the presence of IFN-γ, transcription of gp91-phox was remarkably upregulated, and the cells were differentiated to macrophage-like cells that can produce O2−. Chromatin immunoprecipitation assay using the U937 cells during cultivation with IFN-γ revealed not only that association of GCN5 with the gp91-phox gene promoter was significantly accelerated, but also that GCN5 preferentially elevated acetylation levels of H2BK16 and H3K9 surrounding the promoter. These results suggested that GCN5 regulates the O2−-generating system in leukocytes via controlling the gp91-phox gene expression as a supervisor. Our findings obtained in this study should be useful in understanding the molecular mechanisms involved in epigenetic regulation of the O2−-generating system in leukocytes.
Photobacterium mandapamensis is one of three luminous Photobacterium species able to form species-specific bioluminescent symbioses with marine fishes. Here, we present the draft genome sequence of P. mandapamensis strain svers.1.1, the bioluminescent symbiont of the cardinal fish Siphamia versicolor, the first genome of a symbiotic, luminous Photobacterium species to be sequenced. Analysis of the sequence provides insight into differences between P. mandapamensis and other luminous and symbiotic bacteria in genes involved in quorumsensing regulation of light production and establishment of symbiosis.Photobacterium mandapamensis (Gammaproteobacteria, Vibrionaceae) is the bioluminescent symbiont of the cardinal fish Siphamia versicolor. The fish harbors a dense population of the bacterium in a ventral light organ and uses the bacterial light to attract zooplankton prey. The light organ begins to form early in larval development, through a proliferation and differentiation of intestinal epithelial cells, and it becomes colonized by P. mandapamensis after further larval development (2, 4-8, 11, 14). The specificity of the association and the ability to culture larvae of the fish (5, 8) establish a foundation for experimental analysis of how this vertebrate animal acquires, accommodates, and functions cooperatively with its bacterial symbiont. To begin gaining insight into the genetic interactions underlying the P. mandapamensis-S. versicolor association, we sequenced the genome of P. mandapamensis strain svers.1.1. This is the first genome of a symbiotic, luminous Photobacterium species to be sequenced.The genome of svers.1.1 was sequenced using the Roche 454 GS FLX titanium platform; 310,304 single-end reads and 195,674 paired-end reads were obtained (8-kb fragments), with approximately 36-fold coverage. The sequence reads were initially assembled with GS Assembler software into 31 contigs (Ͼ500 bp).The draft genome is 4,564,780 bp in total, with a GϩC content of 40.76%. The svers.1.1 genome contains two circular chromosomes (as determined by a pulsed-field gel electrophoresis [PFGE] analysis; data not shown), as found in other Vibrionaceae (10). Identification of protein-coding sequences (CDSs) was carried out using the Microbial Genome Annotation Pipeline (MiGAP) (12) with additional information provided by Manatee (IGS Annotation Service [http://manatee .sourceforge.net]). A total of 4,026 CDSs were identified. The genome contains at least six rRNA operons and at least 74 tRNAs.Comparisons were made to genome sequences of other Vibrionaceae to screen for P. mandapamensis genes involved in quorum-sensing regulation of bioluminescence and in symbiosis. A single, vertically inherited lux-rib operon, luxCDABEFGribEBHA (3, 13), was present in the svers.1.1 genome, as were homologs of the regulatory genes cyaA and crp and certain Vibrio harveyi quorum-sensing-regulatory genes, luxO, luxS, luxU, and cqsA. In contrast, homologs of other V. harveyi quorum-sensing-regulatory genes, luxR, luxL, luxM, luxN, luxP, luxQ, a...
Photobacterium leiognathi is a facultative bioluminescent symbiont of marine animals. Strains of P. leiognathi that are merodiploid for the luminescence genes (lux‐rib operon) have been previously obtained only from Japan. In contrast, strains bearing a single lux‐rib operon have been obtained from all the areas sampled in Japan and the western Pacific. In this study, we tested whether distribution of merodiploid P. leiognathi is limited by physical barriers in the environment, or because fish in the western Pacific preferentially form symbiosis with bacteria bearing a single lux‐rib operon. We collected light organ symbionts from Secutor indicius, a fish species that is typically found in the western Pacific and has only recently expanded its geographic range to Japan. We found that all S. indicius specimens collected from Japan formed symbiosis only with single lux‐rib operon‐bearing strains, although fish from other species collected from the same geographic area frequently contained merodiploid strains. This result shows that S. indicius were preferentially colonized by bacteria bearing a single lux‐rib operon and suggests that the limited geographic distribution of merodiploid P. leiognathi can be attributed to preferential colonization of fish species found in the western Pacific by strains bearing only a single lux‐rib operon.
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