Development of novel highly sensitive methods to detect endogenous cGAMP in cells and tissue

Intracellular DNA triggers interferon release during the innate immune response. Cyclic GMP-AMP synthase (cGAS) senses intracellular double-stranded DNA not only in response to viral infection but also under autoimmune conditions. Measuring the levels of cyclic GMP-AMP (cGAMP) as a second messenger of cGAS activation is important to elucidate the physiological and pathological roles of cGAS. Therefore, we generated monoclonal antibodies against cGAMP using hybridoma technology to test antibody specificity and establish methods to detect intracellular cGAMP. The resulting cGAMP-specific antibody enabled the development of a time-resolved fluorescence energy transfer assay with a quantifiable range of 0.1 nM to 100 nM cGAMP. Using this assay, we detected cellular and tissue cGAMP. We confirmed that the cGAMP antibody successfully targeted intracellular cGAMP through immunocytochemical analyses. These results demonstrated that the cGAMP antibody is a powerful tool that allows determining cGAS involvement in autoimmunity and disease pathology at the cell and tissue levels.

Spermatogenesis-specific association of SMCY and MSH5

The status of chromatin during spermatogenesis is dynamically regulated by specific histone codes or stage-specific histone changes. The functional links between such epigenetic regulation and proteins regulating meiosis are largely unknown. In mammals, genes encoded on the Y chromosome are thought to possess male-specific biological functions. While genes located within the azoospermia factor region (AZF) are known to be involved in spermatogenesis, the physiological function of individual genes is not known. SMCY is a gene mapped to the AZF, and in this report, we analyzed the function of SMCY protein during spermatogenesis. Biochemical identification of the proteins with which it interacted showed that SMCY formed a distinct complex with MSH5, a critical meiosis-regulatory protein in the human testicular germ cell line, NEC8. As anticipated, histone H3K4 demethylase activity was detected. Immunohistochemical analysis revealed the co-localization of SMCY with MSH5 at a specific stage of meiotic prophase progression during murine spermatogenesis. Our results suggest that SMCY may have a male-specific function as a histone H3K4 demethylase by recruiting a meiosis-regulatory protein to condensed DNA.

DEAD-box RNA helicase subunits of the Drosha complex are required for processing of rRNA and a subset of microRNAs

MicroRNAs (miRNAs) control cell proliferation, differentiation and fate through modulation of gene expression by partially base-pairing with target mRNA sequences. Drosha is an RNase III enzyme that is the catalytic subunit of a large complex that cleaves pri-miRNAs with distinct structures into pre-miRNAs. Here, we show that both the p68 and p72 DEAD-box RNA helicase subunits in the mouse Drosha complex are indispensable for survival in mice, and both are required for primary miRNA and rRNA processing. Gene disruption of either p68 or p72 in mice resulted in early lethality, and in both p68(-/-) and p72(-/-) embryos, expression levels of a set of, but not all, miRNAs and 5.8S rRNA were significantly lowered. In p72(-/-) MEF cells, expression of p72, but not a mutant lacking ATPase activity, restored the impaired expression of miRNAs and 5.8S rRNA. Furthermore, we purified the large complex of mouse Drosha and showed it could generate pre-miRNA and 5.8S rRNA in vitro. Thus, we suggest that DEAD-box RNA helicase subunits are required for recognition of a subset of primary miRNAs in mDrosha-mediated processing.

Effects of the Escherichia coli sfsA gene on mal genes expression and a DNA binding activity of SfsA

The sfsA gene was identified as one of the sfs genes the over-expression of which stimulates maltose fermentation of the Mal- Escherichia coli strain MK2001 (crp*1, cya:Km(r)). Expression from the malPQ promoter, which was measured using a chromosomally integrated malPp-lacZ fusion, was induced by over-expressing the sfsA gene in the crp*1, cya:Km(r) strain. The level of the MalE protein was increased in crp*1, cya:Km(r) cells over-producing SfsA. The SfsA protein was purified to homogeneity and tested for DNA binding activity. The purified SfsA protein binds to DNA non-specifically. All these results may suggest that SfsA functions as a DNA binding protein to induce the mal genes in coordination with CRP*1.

Synergistic effect of active oxygen species and alginate on chitinase production by Wasabia japonica cells and its application

The specific chitinase productivity of a Wasabia japonica cell suspension culture under pure oxygen aeration was 3.8 times higher than that of a suspension culture aerated with ordinary air. During aeration with pure oxygen, both oxygen consumption by the cells and the H2O2 concentration in the medium increased. Addition of H2O2 to the cultivation medium also promoted the specific chitinase productivity. H2O2 could pass freely through the cell membrane. It was assumed that the excess oxygen was converted into active oxygen species such as H2O2, and that the promotion of chitinase production was probably due to the generated active oxygen species. Addition of alginate oligomer (AO, an endogenous elicitor-like substance) to cultures aerated with pure oxygen or supplemented with H2O2 resulted in synergistic increases in chitinase production. Based on these results, the development of a simple and efficient chitinase production system was investigated. Cells were immobilized in alginate gel (instead of adding AO to the medium) and cultivated in a medium containing H2O2. The specific chitinase productivity increased to the levels observed in the suspension culture system. During repeated batch cultivation of immobilized cells, the chitinase production remained stable for three repeated batches. When immobilized protoplasts were cultivated in a medium containing H2O2, there was 7-fold increase in chitinase production compared with that of immobilized cells.