The energy that sustains cancer cells is derived preferentially from glycolysis. This metabolic change, the Warburg effect, was one of the first alterations in cancer cells recognized as conferring a survival advantage. Here, we show that p53, one of the most frequently mutated genes in cancers, modulates the balance between the utilization of respiratory and glycolytic pathways. We identify Synthesis of Cytochrome c Oxidase 2 (SCO2) as the downstream mediator of this effect in mice and human cancer cell lines. SCO2 is critical for regulating the cytochrome c oxidase (COX) complex, the major site of oxygen utilization in the eukaryotic cell. Disruption of the SCO2 gene in human cancer cells with wild-type p53 recapitulated the metabolic switch toward glycolysis that is exhibited by p53-deficient cells. That SCO2 couples p53 to mitochondrial respiration provides a possible explanation for the Warburg effect and offers new clues as to how p53 might affect aging and metabolism.

A previous bioinformatics-based search for small RNAs in Escherichia coli identified a novel RNA named IS183. The gene encoding this small RNA is located between and on the opposite strand of genes encoding two transcriptional regulators of the acid response, gadX (yhiX) and gadW (yhiW). Given that IS183 is encoded in the gad gene cluster and because of its role in regulating acid response genes reported here, this RNA has been renamed GadY. We show that GadY exists in three forms, a long form consisting of 105 nucleotides and two processed forms, consisting of 90 and 59 nucleotides. The expression of this small RNA is highly induced during stationary phase in a manner that is dependent on the alternative sigma factor S . Overexpression of the three GadY RNA forms resulted in increased levels of the mRNA encoding the GadX transcriptional activator, which in turn caused increased levels of the GadA and GadB glutamate decarboxylases. A promoter mutation which abolished gadY expression resulted in a reduction in the amount of gadX mRNA during stationary phase. The gadY gene was shown to overlap the 3 end of the gadX gene, and this overlap region was found to be necessary for the GadY-dependent accumulation of gadX mRNA. We suggest that during stationary phase, GadY forms base pairs with the 3-untranslated region of the gadX mRNA and confers increased stability, allowing for gadX mRNA accumulation and the increased expression of downstream acid resistance genes.

Rationale: Exercise capacity is a physiological characteristic associated with protection from both cardiovascular and all-cause mortality. p53 regulates mitochondrial function and its deletion markedly diminishes exercise capacity, but the underlying genetic mechanism orchestrating this is unclear. Understanding the biology of how p53 improves exercise capacity may provide useful insights for improving both cardiovascular as well as general health. Objective: The purpose of this study was to understand the genetic mechanism by which p53 regulates aerobic exercise capacity. Methods and Results: Using a variety of physiological, metabolic, and molecular techniques, we further characterized maximum exercise capacity and the effects of training, measured various nonmitochondrial and mitochondrial determinants of exercise capacity, and examined putative regulators of mitochondrial biogenesis.As p53 Key Words: aerobic Ⅲ exercise Ⅲ mitochondrial DNA Ⅲ p53 Ⅲ TFAM A cross populations aerobic exercise capacity inversely correlates with cardiovascular disease and all-cause mortality. 1-3 Our report of a marked reduction in the maximal exercise capacity of p53 homozygous knockout (p53 Ϫ/Ϫ ) mice and subsequent confirmation by others provided physiological evidence for p53 as an important mediator of aerobic metabolism. 4,5 We previously showed that p53 promotes mitochondrial respiration in human and murine cells by regulating the transcription of Synthesis of Cytochrome c Oxidase 2 (SCO2), a gene essential for oxidative phosphorylation. 4,6 A concurrent report demonstrating that p53 directly suppresses glycolysis through TIGAR, a p53-dependent regulator of glycolysis and apoptosis, suggested that p53 can coordinate aerobic and glycolytic metabolism. 7 Multiple factors contribute to aerobic exercise capacity, but one major determinant is the mitochondrial content of skeletal muscle as demonstrated by a genetic selection experiment. 8 A recent study showed decreased mitochondrial density in the skeletal muscle of p53-deficient mice, 5 but the genetic mechanism orchestrating this change has remained unclear. A number of other studies have also associated p53 with exercise response and mitochondrial function. For example, p53 levels are increased after acute exercise, and the transition from glycolysis to oxidative metabolism during development is dependent on p53. 9,10 p53 can transactivate ribonucleotide reductase p53R2 (RRM2B) which is important for maintaining mtDNA in skeletal muscle. 11 Additionally, 2 recent studies have shown asso-

Nucleosome Remodeling Factor (NURF) is an ATP-dependent nucleosome remodeling complex that alters chromatin structure by catalyzing nucleosome sliding, thereby exposing DNA sequences previously associated with nucleosomes. We systematically studied how the unstructured N-terminal residues of core histones (the N-terminal histone tails) influence nucleosome sliding. We used bacterially expressed Drosophila histones to reconstitute hybrid nucleosomes lacking one or more histone N-terminal tails. Unexpectedly, we found that removal of the N-terminal tail of histone H2B promoted uncatalyzed nucleosome sliding during native gel electrophoresis. Uncatalyzed nucleosome mobility was enhanced by additional removal of other histone tails but was not affected by hyperacetylation of core histones by p300. In addition, we found that the N-terminal tail of the histone H4 is specifically required for ATP-dependent catalysis of nucleosome sliding by NURF. Alanine scanning mutagenesis demonstrated that H4 residues 16-KRHR-19 are critical for the induction of nucleosome mobility, revealing a histone tail motif that regulates NURF activity. An exchange of histone tails between H4 and H3 impaired NURF-induced sliding of the mutant nucleosome, indicating that the location of the KRHR motif in relation to global nucleosome structure is functionally important. Our results provide functions for the N-terminal histone tails in regulating the mobility of nucleosomes.T he genome of eukaryotes is packaged into chromatin. The fundamental building block of chromatin is the nucleosome core particle, in which 147 bp of DNA is wrapped around a histone octamer in a left-handed superhelix (1). Chromatin structure plays a major role in processes such as transcription (2). Recent advances have revealed that chromatin structure is highly dynamic and subject to reversible changes in higher-order folding and nucleosome positioning (3, 4). These structural changes are largely mediated by enzymatic covalent modifications of the flexible N-terminal amino acids of the core histones and by noncovalent alterations of nucleosome architecture driven by ATP-dependent chromatin remodeling enzymes (3, 4).Four classes of ATP-dependent chromatin remodeling complexes, each containing a member of the SWI2͞SNF2 family of ATPases, have been characterized (4-8). Complexes containing SWI2͞SNF2 or its highly related paralog STH1 (the SWI͞SNF and RSC complexes) have been demonstrated to play a role in transcription (9-13). Complexes containing ISWI, Mi-2, and INO80 ATPases are also implicated in transcription and possibly other DNA transactions (14-18). Chromatin remodeling complexes that contain the ISWI ATPase include Nucleosome Remodeling Factor (NURF), ACF, CHRAC, RSF, WCRF, ISWI-B, and ISWI-D complexes in metazoans, and the Isw1 and Isw2 complexes in budding yeast (19)(20)(21)(22)(23)(24)(25)(26)(27)(28). ISWI complexes remodel chromatin by mediating nucleosome ''sliding,'' the relative movement of a histone octamer in cis, without irretrievable displacement from DNA...

Oxygen is not only required for oxidative phosphorylation but also serves as the essential substrate for the formation of reactive oxygen species (ROS), which is implicated in ageing and tumorigenesis. Although the mitochondrion is known for its bioenergetic function, the symbiotic theory originally proposed that it provided protection against the toxicity of increasing oxygen in the primordial atmosphere. Using human cells lacking Synthesis of Cytochrome c Oxidase 2 (SCO2 –/–), we have tested the oxygen toxicity hypothesis. These cells are oxidative phosphorylation defective and glycolysis dependent; they exhibit increased viability under hypoxia and feature an inverted growth response to oxygen compared with wild-type cells. SCO2 –/– cells have increased intracellular oxygen and nicotinamide adenine dinucleotide (NADH) levels, which result in increased ROS and oxidative DNA damage. Using this isogenic cell line, we have revealed the genotoxicity of ambient oxygen. Our study highlights the importance of mitochondrial respiration both for bioenergetic benefits and for maintaining genomic stability in an oxygen-rich environment.

SUMMARY There is growing evidence that alterations in metabolism may contribute to tumorigenesis. Here, we report on members of families with the Li–Fraumeni syndrome who carry germline mutations in TP53, the gene encoding the tumor-suppressor protein p53. As compared with family members who are not carriers and with healthy volunteers, family members with these mutations have increased oxidative phosphorylation of skeletal muscle. Basic experimental studies of tissue samples from patients with the Li–Fraumeni syndrome and a mouse model of the syndrome support this in vivo finding of increased mitochondrial function. These results suggest that p53 regulates bioenergetic homeostasis in humans. (Funded by the National Heart, Lung, and Blood Institute and the National Institutes of Health; ClinicalTrials.gov number, NCT00406445.)

p53, a critical tumor suppressor, regulates mitochondrial respiration, but how a nuclear protein can orchestrate the function of an organelle encoded by two separate genomes, both of which require p53 for their integrity, remains unclear. Here we report that the mammalian homolog of the yeast mitochondrial disulfide relay protein Mia40 (CHCHD4) is necessary for the respiratorydependent translocation of p53 into the mitochondria. In the setting of oxidative stress, increased CHCHD4 expression partitions p53 into the mitochondria and protects its genomic integrity while decreasing p53 nuclear localization and transcriptional activity. Conversely, decreased CHCHD4 expression prevents the mitochondrial translocation of p53 while augmenting its nuclear localization and activity. Thus, the mitochondrial disulfide relay system allows p53 to regulate two spatially segregated genomes depending on oxidative metabolic activity.mitochondrial DNA | DNA repair | mutant p53

Circulating monocytes mediate inflammation in atherosclerosis and may serve as easily accessible reporters of disease. To search for markers of atherosclerosis, we compared the in vivo transcriptomes of monocytes purified from patients undergoing carotid endarterectomy and normal subjects by using the serial analysis of gene expression technique. We selected a subset of differentially expressed monocyte-specific genes and confirmed their expression levels. The Finkel-Biskis-Jinkins osteosarcoma (FOS) gene was significantly increased in patients, and the highest levels of FOS associated with patients who had previously undergone coronary revascularization. The correlation between coronary revascularization and FOS was higher than that compared with the cardiac risk marker high sensitivity C-reactive protein. In vitro inhibition of FOS using small interfering RNA and 3-hydroxy-3-methyl-glutaryl CoA reductase inhibitor simvastatin (statin) affected monocyte activation and suggested an important role in pathogenesis. Given the prominent role of FOS in inflammation and calcification, its association with atherosclerosis severity has clear pathophysiologic bases as well as clinical implications as a marker. Our results suggest that analysis of gene expression in circulating cells may provide biological and clinical insights into human atherosclerosis, and that this type of approach may be applicable for studying other types of diseases.monocytes ͉ serial analysis of gene expression ͉ Finkel-Biskis-Jinkins osteosarcoma ͉ 3-hydroxy-3-methyl-glutaryl CoA reductase inhibitor ͉ high sensitivity C-reactive protein