Mitochondriogenesis in synchronous cultures of yeast. I. Oscillatory pattern of respiration

Synchronised cultures of yeast, Saccharomyces cerevisiae provide ideal material for the study of mitochondria. While studying the oxygen uptake capacity of synchronously growing cultures, it was noticed that oxygen uptake increased and decreased in an oscillatory pattern. Such a pattern was repeated up to four cycles. This observed behavior is entirely different from the results reported earlier by others.     

DnaK expression in response to heat shock of Streptococcus mutans

Abstract The oral pathogen, Streptococcus mutans , persistently colonizes human hosts and initiates oral disease despite extreme variations in environmental conditions. To begin to investigate the role of the stress protein, DnaK (Hsp70), in environmental stress responses by S. mutans , pulse—chase experiments were initially used to establish that a functional heat shock response existed in this organism. A C-terminal fragment of the S. mutans dnaK gene was cloned and engineered to be expressed with a histidine tag. Using the recombinant DnaK protein that had been purified by nickel affinity chromatography, an antibody specific for the S. mutans DnaK protein was generated to analyse DnaK expression under homeostatic and heat shock conditions. Western blot analysis indicated that the anti-recombinant DnaK antibody specifically recognized a protein (molecular mass approx. 68 kDa) which was induced in response to thermal stress. Elucidating the role of DnaK in responses by S. mutans to various environmental Stressors will provide a better understanding of how DnaK is involved in survival of extreme environments and the contribution of the DnaK protein to the virulence of S. mutans .     

Role of cyclic AMP in mitochondriogenesis in yeast

Cyclic AMP prevents the release of proteins from mitochondria (prelabelled with radioactive aminoacids) during glucose repression in yeast cells and chloramphenicol has no effect on this process. Using specific antisera, the release of the mitochondrially synthesised membrane factor of ATPase during repression and the blocking of this by cAMP has been demonstrated.     

Proteolysis of Apolipoprotein A-I by Secretory Phospholipase A2: A NEW LINK BETWEEN INFLAMMATION AND ATHEROSCLEROSIS*

In the acute phase of the inflammatory response, secretory phospholipase A₂ (sPLA₂) reaches its maximum levels in plasma, where it is mostly associated with high density lipoproteins (HDL). Overexpression of human sPLA₂ in transgenic mice reduces both HDL cholesterol and apolipoprotein A-I (apoA-I) plasma levels through increased HDL catabolism by an unknown mechanism. To identify unknown PLA₂-mediated activities on the molecular components of HDL, we characterized the protein and lipid products of the PLA₂ reaction with HDL. Consistent with previous studies, hydrolysis of HDL phospholipids by PLA₂ reduced the particle size without changing its protein composition. However, when HDL was destabilized in the presence of PLA₂ by the action of cholesteryl ester transfer protein or by guanidine hydrochloride treatment, a fraction of apoA-I, but no other proteins, dissociated from the particle and was rapidly cleaved. Incubation of PLA₂ with lipid-free apoA-I produced similar protein fragments in the range of 6–15 kDa, suggesting specific and direct reaction of PLA₂ with apoA-I. Mass spectrometry analysis of isolated proteolytic fragments indicated at least two major cleavage sites at the C-terminal and the central domain of apoA-I. ApoA-I proteolysis by PLA₂ was Ca²⁺-independent, implicating a different mechanism from the Ca²⁺-dependent PLA₂-mediated phospholipid hydrolysis. Inhibition of proteolysis by benzamidine suggests that the proteolytic and lipolytic activities of PLA₂ proceed through different mechanisms. Our study identifies a previously unknown proteolytic activity of PLA₂ that is specific to apoA-I and may contribute to the enhanced catabolism of apoA-I in inflammation and atherosclerosis.     

Approaches to Enhance the Binding Affinity and Nuclease Stability of Triplex Forming Oligonucleotides

Abstract

The ability of simple azole nucleosides to promote antiparallel triplex formation at non-homopurine duplex targets was explored. It was also shown that spermidine-cholesterol conjugation is effective in enhancing cellular uptake and stability of oligonucleotides.     

A simple method to study microbial coal solubilization using Pluronic F-127-amended media

Summary Microbial coal solubilization and the extraction of solubilized coal products were carried out in media amended with polyol (Pluronic F-127), an agent which gels above 18°C but reverts to a liquid state at low temperature (4°C). The solubilized coal products, the unsolubilized coal particles and the mycelial mat were separated effectively by centrifugation at 4°C. The amount of coal solubilization was 30–50% higher in polyol-amended media than in agar media regardless of the microorganism. On the other hand, the amount of coal solubilization in polyol-amended control media was less compared to agar-amended control media.     

ΔNp63α is an oncogene that targets chromatin remodeler Lsh to drive skin stem cell proliferation and tumorigenesis

The p53 homolog p63 is essential for development, yet its role in cancer is not clear. We discovered that p63 deficiency evokes the tumor-suppressive mechanism of cellular senescence, causing a striking absence of stratified epithelia such as the skin. Here we identify the predominant p63 isoform, ΔNp63α, as a protein that bypasses oncogene-induced senescence to drive tumorigenesis in?vivo. Interestingly, bypass of senescence promotes stem-like proliferation and maintains survival of the keratin 15-positive stem cell population. Furthermore, we identify the chromatin-remodeling protein Lsh as a new target of ΔNp63α that is an essential mediator of senescence bypass. These findings indicate that ΔNp63α is an oncogene that cooperates with Ras to promote tumor-initiating stem-like proliferation and suggest that Lsh-mediated chromatin-remodeling events are critical to this process.