Yin Yang 1 Orchestrates a Metabolic Program Required for Both Neural Crest Development and Melanoma Formation

Increasing evidence suggests that cancer cells highjack developmental programs for disease initiation and progression. Melanoma arises from melanocytes that originate during development from neural crest stem cells (NCSCs). Here, we identified the transcription factor Yin Yang 1 (Yy1) as an NCSCs regulator. Conditional deletion of Yy1 in NCSCs resulted in stage-dependent hypoplasia of all major neural crest derivatives due to decreased proliferation and increased cell death. Moreover, conditional ablation of one Yy1 allele in a melanoma mouse model prevented tumorigenesis, indicating a particular susceptibility of melanoma cells to reduced Yy1 levels. Combined RNA sequencing (RNA-seq), chromatin immunoprecipitation (ChIP)-seq, and untargeted metabolomics demonstrated that YY1 governs multiple metabolic pathways and protein synthesis in both NCSCs and melanoma. In addition to directly regulating a metabolic gene set, YY1 can act upstream of MITF/c-MYC as part of a gene regulatory network controlling metabolism. Thus, both NCSC development and melanoma formation depend on an intricate YY1-controlled metabolic program.

Differential effects of peripheral and brain tumor necrosis factor on inflammation, sickness, emotional behavior and memory in mice

Tumor necrosis factor alpha (TNF) is increased in depression and clinical-trial evidence indicates that blocking peripheral TNF has some antidepressant efficacy. In rodents, peripheral or intracerebroventricular TNF results in sickness e.g. reduced body weight, altered emotional behavior and impaired memory. However, the underlying pathways and responsible brain regions are poorly understood. The aim of this mouse study was to increase understanding by comparing the effects of sustained increases in TNF in the circulation, in brain regions impacted by increased circulating TNF, or specific brain regions. Increased peripheral TNF achieved by repeated daily injection (IP-TNF) or osmotic pump resulted in decreased body weight, decreased saccharin (reward) consumption, and increased memory of an aversive conditioned stimulus. These effects co-occurred with increased plasma interleukin-6 and increased IP-derived TNF in brain peri-ventricular regions. An adenovirus-associated viral TNF vector (AAV-TNF) was constructed, brain injection of which resulted in dose-dependent, sustained and region-specific TNF expression, and was without effect on blood cytokine levels. Lateral ventricle AAV-TNF yielded increased TNF in the same brain regions as IP-TNF. In contrast to IP-TNF it was without effect on body weight, saccharin consumption and fear memory, although it did increase anxiety. Hippocampal AAV-TNF led to decreased body weight. It increased conditioning to but not subsequent memory of an aversive context, suggesting impaired consolidation; it also increased anxiety. Amygdala AAV-TNF was without effect on body weight and aversive stimulus learning-memory, but reduced saccharin consumption and increased anxiety. This study adds significantly to the evidence that both peripheral and brain region-specific increases in TNF lead to both sickness and depression- and anxiety disorder-relevant behavior and do so via different pathways. It thereby highlights the complexity in terms of indirect and direct pathways via which increased TNF can act and which need to be taken into account when considering it as a therapeutic target.

Antimicrobial activities of chemically modified thiazolyl peptide antibiotic MDL 62,879 (GE2270A)

MDL 62,879 (GE2270A) 1 is a new inhibitor of elongation factor-Tu (EF-Tu) and belongs to the class of thiazolyl peptide antibiotics. Controlled acid hydrolysis of 1 followed by treatment with base resulted in the lost of the two terminal amino acids and in the formation of water-soluble MDL 62,935 2. Although less active in vitro than its parent compound, 2 was able to inhibit by 50% an Escherichia coli cell-free protein synthesis system at roughly the same concentration of 1. MDL 62,935 2 was subjected to further modification at the beta-phenylserine residue. Derivatives obtained from 2 were less active in both antimicrobial (MIC) and enzymatic (IC50) assays. This suggests that beta-phenylserine plays an important role for the inhibition of EF-Tu by 1 and 2.

Antibiotics MDL 62,879 and kirromycin bind to distinct and independent sites of elongation factor Tu (EF-Tu)

Antibiotic MDL 62,879 inhibits bacterial protein synthesis by acting on elongation factor Tu (EF-Tu). In this study we show that the inhibition of protein synthesis by MDL 62,879 in an Escherichia coli cell-free system was fully reversed by addition of stoichiometric amounts of EF-Tu but not by large excesses of EF-Ts, ribosomes, or aa-tRNA. MDL 62,879 bound tightly to EF-Tu and formed a stable 1:1 MDL 62,879:EF-Tu (M:EF-Tu) complex. We show that binding of MDL 62,879 to EF-Tu strongly affects the interaction of EF-Tu with aa-tRNA and causes rapid dissociation of preformed EF-Tu.aa-tRNA complex, suggesting that inhibition of aa-tRNA binding is due to a conformational change in EF-Tu rather than competition for the aa-tRNA binding site. Indication of a conformational change in EF-Tu induced by MDL 62,879 is further confirmed by proteolytic cleavage experiments: MDL 62,879 binding strongly protects EF-Tu against trypsin cleavage. The observed effects of MDL 62,879 appear to be different from those of the kirromycin class of antibiotics, which also inhibit protein synthesis by binding to EF-Tu, suggesting two distinct binding sites. Indeed, the M:EF-Tu complex was able to bind stoichiometric amounts of kirromycin to form a 1:1:1 M:EF-Tu:kirromycin (M:EF-Tu:K) complex, providing direct evidence that the two antibiotics bind to independent and distinct sites on the EF-Tu molecule. The interaction of the M:EF-Tu:K complex with aa-tRNA and other co-factors suggest that the contemporary binding of the two antibiotics locks EF-Tu into an intermediate conformation in which neither antibiotic exhibits complete dominance.