A nonribosomal peptide synthetase (NRPS) gene cluster (sfa) was identified in Streptomyces thioluteus to direct the biosynthesis of the diisonitrile antibiotic SF2768. Its biosynthetic pathway was reasonably proposed based on bioinformatics analysis, metabolic profiles of mutants, and the elucidation of the intermediate and shunt product structures. Bioinformatics-based alignment found a putative ATP-binding cassette (ABC) transporter related to iron import within the biosynthetic gene cluster, which implied that the product might be a siderophore. However, characterization of the metal-binding properties by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), metal-ligand titration, thin-layer chromatography (TLC), and chrome azurol S (CAS) assays revealed that the final product SF2768 and its diisonitrile derivatives specifically bind copper, rather than iron, to form stable complexes. Inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed that the intracellular cupric content of S. thioluteus significantly increased upon incubation with the copper-SF2768 complex, direct evidence for the copper acquisition function of SF2768. Further in vivo functional characterization of the transport elements for the copper-SF2768 complexes not only confirmed the chalkophore identity of the compound but also gave initial clues into the copper uptake mechanism of this nonmethanotrophic microorganism.

Expression of DAZ-like (DAZL) is a hallmark of vertebrate germ cells, and is essential for embryonic germ cell development and differentiation, yet the gametogenic function of DAZL has not been fully characterized and most of its in vivo direct targets remain unknown. We showed that postnatal stage-specific deletion of Dazl in mouse germ cells did not affect female fertility, but caused complete male sterility with gradual loss of spermatogonial stem cells, meiotic arrest and spermatid arrest. Using the genome-wide high-throughput sequencing of RNAs isolated by cross-linking immunoprecipitation and mass spectrometry approach, we found that DAZL bound to a large number of testicular mRNA transcripts (at least 3008) at the 3′-untranslated region and interacted with translation proteins including poly(A) binding protein. In the absence of DAZL, polysome-associated target transcripts, but not their total transcripts, were significantly decreased, resulting in a drastic reduction of an array of spermatogenic proteins and thus developmental arrest. Thus, DAZL is a master translational regulator essential for spermatogenesis.

The expression of PD-L1 in tumor cells is one of the main causes of tumor immune escape. However, the exact mechanism for regulating PD-L1 expression in gastric cancer (GC) cells remains unclear. Our previous studies have shown that mesenchymal stem cells (MSCs) exert broad immunosuppressive potential, modulating the activity of cells either in innate or adaptive immune system to promote tumor progress. This study aims to investigate whether GCMSCs regulate the PD-L1 expression in GC cells and explore the specific molecular mechanism. The results have shown that GCMSCs enhanced PD-L1 expression in GC cells resulting in the resistance of GC cells to CD8+ T cells cytotoxicity. However, this resistance was attenuated with IL-8 inhibition. Further studies proved that IL-8 derived from GCMSCs induced PD-L1 expression in GC cells via c-Myc regulated by STAT3 and mTOR signaling pathways. Our data indicated that blocking IL-8 derived from GCMSCs may overcome the immune escape induced by PD-L1 in GC cells and provide a potential strategy to enhance the immunotherapy efficiency in GC.

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