Expression of micF involved in porin synthesis in Escherichia coli: two distinct cis-acting elements respectively regulate micF expression positively and negatively

micF RNA, whose sequence is highly complementary to a 5'-portion of ompF mRNA, has been implicated in the osmoregulation and thermoregulation of the ompF porin gene in Escherichia coli. To define and characterize cis-acting regulatory regions upstream of the micF promoter, a series of deletions of the micF promoter fused to the lacZ gene were constructed. Two distinct regions, which function differently, were identified as cis-acting regulatory elements, namely, one responsible for OmpR-dependent activation and the other for OmpR-independent repression of micF expression. The former contains the OmpR-binding site, which simultaneously regulates both the genes, micF and ompC, in response to the medium osmolarity. The latter may be involved in an unknown regulatory process of micF expression.     

Amino acid sequence of photosystem I subunit IV from the cyanobacterium Synechocystis PCC 6803

We describe here the complete amino acid sequence of photosystem I subunit IV from Synechocystis 6803. The molecular mass of 8.0 kDa is lower than in higher plants and Chlamydomonas, due to the lack of a characteristic, proline-rich, N-terminal sequence. The remaining sequence exhibits a good conservation, with a hydrophilic and strongly basic N-tenninal head followed by two hydrophobic domains. There is no possibility of classical membrane-spanning alpha helices. This component is likely to be one of the most stroma accessible subunits of photosystem I.     

Phenotypic and genetic relationships between growth and feed intake curves and feed efficiency and amino acid requirements in the growing pig

Improvement of feed efficiency in pigs has been achieved essentially by increasing lean growth rate, which resulted in lower feed intake (FI). The objective was to evaluate the impact of strategies for improving feed efficiency on the dynamics of FI and growth in growing pigs to revisit nutrient recommendations and strategies for feed efficiency improvement. In 2010, three BWs, at 35±2, 63±9 and 107±7 kg, and daily FI during this period were recorded in three French test stations on 379 Large White and 327 French Landrace from maternal pig populations and 215 Large White from a sire population. Individual growth and FI model parameters were obtained with the InraPorc^R software and individual nutrient requirements were computed. The model parameters were explored according to feed efficiency as measured by residual feed intake (RFI) or feed conversion ratio (FCR). Animals were separated in groups of better feed efficiency (RFI⁻ or FCR⁻), medium feed efficiency and poor feed efficiency. Second, genetic relationships between feed efficiency and model parameters were estimated. Despite similar average daily gains (ADG) during the test for all RFI groups, RFI⁻ pigs had a lower initial growth rate and a higher final growth rate compared with other pigs. The same initial growth rate was found for all FCR groups, but FCR⁻ pigs had significantly higher final growth rates than other pigs, resulting in significantly different ADG. Dynamic of FI also differed between RFI or FCR groups. The calculated digestible lysine requirements, expressed in g/MJ net energy (NE), showed the same trends for RFI or FCR groups: the average requirements for the 25% most efficient animals were 13% higher than that of the 25% least efficient animals during the whole test, reaching 0.90 to 0.95 g/MJ NE at the beginning of the test, which is slightly greater than usual feed recommendations for growing pigs. Model parameters were moderately heritable (0.30±0.13 to 0.56±0.13), except for the precocity of growth (0.06±0.08). The parameter representing the quantity of feed at 50 kg BW showed a relatively high genetic correlation with RFI (0.49±0.14), and average protein deposition between 35 and 110 kg had the highest correlation with FCR (−0.76±0.08). Thus, growth and FI dynamics may be envisaged as breeding tools to improve feed efficiency. Furthermore, improvement of feed efficiency should be envisaged jointly with new feeding strategies.     

Endoplasmic reticulum stress in insulin resistance and diabetes

The endoplasmic reticulum is the main intracellular Ca²⁺ store for Ca²⁺ release during cell signaling. There are different strategies to avoid ER Ca²⁺ depletion. Release channels utilize first Ca²⁺-bound to proteins and this minimizes the reduction of the free luminal [Ca²⁺]. However, if release channels stay open after exhaustion of Ca²⁺-bound to proteins, then the reduction of the free luminal ER [Ca²⁺] (via STIM proteins) activates Ca²⁺ entry at the plasma membrane to restore the ER Ca²⁺ load, which will work provided that SERCA pump is active. Nevertheless, there are several noxious conditions that result in decreased activity of the SERCA pump such as oxidative stress, inflammatory cytokines, and saturated fatty acids, among others. These conditions result in a deficient restoration of the ER [Ca²⁺] and lead to the ER stress response that should facilitate recovery of the ER. However, if the stressful condition persists then ER stress ends up triggering cell death and the ensuing degenerative process leads to diverse pathologies; particularly insulin resistance, diabetes and several of the complications associated with diabetes. This scenario suggests that limiting ER stress should decrease the incidence of diabetes and the mobility and mortality associated with this illness.     

Novel Interaction of the Z-DNA Binding Domain of Human ADAR1 with the Oncogenic c-Myc Promoter G-Quadruplex

Both G-quadruplex and Z-DNA can be formed in G-rich and repetitive sequences on genome, and their formation and biological functions are controlled by specific proteins. Z-DNA binding proteins, such as human ADAR1, have a highly conserved Z-DNA binding domain having selective affinity to Z-DNA. Here, our study identifies the Z-DNA binding domain of human ADAR1 (hZα_ADAR1) as a novel G-quadruplex binding protein that recognizes c-myc promoter G-quadruplex formed in NHEIII₁ region and represses the gene expression. An electrophoretic migration shift assay shows the binding of hZα_ADAR1 to the intramolecular c-myc promoter G-quadruplex-forming DNA oligomer. To corroborate the binding of hZα_ADAR1 to the G-quadruplex, we conducted CD and NMR chemical shift perturbation analyses. CD results indicate that hZα_ADAR1 stabilizes the parallel-stranded conformation of the c-myc G-quadruplex. The NMR chemical shift perturbation data reveal that the G-quadruplex binding region in hZα_ADAR1 was almost identical with the Z-DNA binding region. Finally, promoter assay and Western blot analysis show that hZα_ADAR1 suppresses the c-myc expression promoted by NHEIII₁ region containing the G-quadruplex-forming sequence. This finding suggests a novel function of Z-DNA binding protein as a regulator of G-quadruplex-mediated gene expression.