RNA helicases and abiotic stress

RNA helicases function as molecular motors that rearrange RNA secondary structure, potentially performing roles in any cellular process involving RNA metabolism. Although RNA helicase association with a range of cellular functions is well documented, their importance in response to abiotic stress is only beginning to emerge. This review summarizes the available data on the expression, biochemistry and physiological function(s) of RNA helicases regulated by abiotic stress. Examples originate primarily from non-mammalian organisms while instances from mammalian sources are restricted to post-translational regulation of helicase biochemical activity. Common emerging themes include the requirement of a cold-induced helicase in non-homeothermic organisms, association and regulation of helicase activity by stress-induced phosphorylation cascades, altered nuclear–cytoplasmic shuttling in eukaryotes, association with the transcriptional apparatus and the diversity of biochemical activities catalyzed by a subgroup of stress-induced helicases. The data are placed in the context of a mechanism for RNA helicase involvement in cellular response to abiotic stress. It is proposed that stress-regulated helicases can catalyze a nonlinear, reversible sequence of RNA secondary structure rearrangements which function in RNA maturation or RNA proofreading, providing a mechanism by which helicase activity alters the activation state of target RNAs through regulation of the reaction equilibrium

Cell surface acid-base properties of the cyanobacterium Synechococcus: Influences of nitrogen source, growth phase and N:P ratios

The distribution of many trace metals in the oceans is controlled by biological uptake. Recently, Liu et al. (2015) demonstrated the propensity for a marine cyanobacterium to adsorb cadmium from seawater, suggesting that cell surface reactivity might also play an important role in the cycling of metals in the oceans. However, it remains unclear how variations in cyanobacterial growth rates and nutrient supply might affect the chemical properties of their cellular surfaces. In this study we used potentiometric titrations and Fourier Transform Infrared (FT-IR) spectrometry to profile the key metabolic changes and surface chemical responses of a Synechococcus strain, PCC 7002, during different growth regimes. This included testing various nitrogen (N) to phosphorous (P) ratios (both nitrogen and phosphorous dependent), nitrogen sources (nitrate, ammonium and urea) and growth stages (exponential, stationary, and death phase). FT-IR spectroscopy showed that varying the growth substrates on which Synechococcus cells were cultured resulted in differences in either the type or abundance of cellular exudates produced or a change in the cell wall components. Potentiometric titration data were modeled using three distinct proton binding sites, with resulting pKa values for cells of the various growth conditions in the ranges of 4.96-5.51 (pKa1), 6.67-7.42 (pKa2) and 8.13-9.95 (pKa3). According to previous spectroscopic studies, these pKa ranges are consistent with carboxyl, phosphoryl, and amine groups, respectively. Comparisons between the titration data (for the cell surface) and FT-IR spectra (for the average cellular changes) generally indicate (1) that the nitrogen source is a greater determinant of ligand concentration than growth phase, and (2) that phosphorus limitation has a greater impact on Synechococcus cellular and extracellular properties than does nitrogen limitation. Taken together, these techniques indicate that nutritional quality during cell growth can noticeably influence the expression of cell surface ligands and their measurable densities. Given that cell surface charge ultimately affects metal adsorption, our results suggest that the cycling of metals by Synechococcus cells in the oceans may vary regionally

Dead-box proteins: a family affair—active and passive players in RNP-remodeling

DEAD-box proteins are characterized by nine conserved motifs. According to these criteria, several hundreds of these proteins can be identified in databases. Many different DEAD-box proteins can be found in eukaryotes, whereas prokaryotes have small numbers of different DEAD-box proteins. DEAD-box proteins play important roles in RNA metabolism, and they are very specific and cannot mutually be replaced. In vitro, many DEAD-box proteins have been shown to have RNA-dependent ATPase and ATP-dependent RNA helicase activities. From the genetic and biochemical data obtained mainly in yeast, it has become clear that these proteins play important roles in remodeling RNP complexes in a temporally controlled fashion. Here, I shall give a general overview of the DEAD-box protein family

Renewable energy from Cyanobacteria: energy production optimization by metabolic pathway engineering

The need to develop and improve sustainable energy resources is of eminent importance due to the finite nature of our fossil fuels. This review paper deals with a third generation renewable energy resource which does not compete with our food resources, cyanobacteria. We discuss the current state of the art in developing different types of bioenergy (ethanol, biodiesel, hydrogen, etc.) from cyanobacteria. The major important biochemical pathways in cyanobacteria are highlighted, and the possibility to influence these pathways to improve the production of specific types of energy forms the major part of this review

SURVEY AND SUMMARY RNA helicases and abiotic stress

RNA helicases function as molecular motors that rearrange RNA secondary structure, potentially performing roles in any cellular process involving RNA metabolism. Although RNA helicase association with a range of cellular functions is well documented, their importance in response to abiotic stress is only beginning to emerge. This review summarizes the available data on the expression, biochemistry and physiological function(s) of RNA helicases regulated by abiotic stress. Examples originate primarily from non-mammalian organisms while instances from mammalian sources are restricted to post-translational regulation of helicase biochemical activity. Common emerging themes include the requirement of a cold-induced helicase in non-homeothermic organisms, association and regulation of helicase activity by stress-induced phosphorylation cascades, altered nuclear– cytoplasmic shuttling in eukaryotes, association with the transcriptional apparatus and the diversity of biochemical activities catalyzed by a subgroup of stress-induced helicases. The data are placed in the context of a mechanism for RNA helicase involvement in cellular response to abiotic stress. It is proposed that stress-regulated helicases can catalyze a nonlinear, reversible sequence of RNA secondary structure rearrangements which function in RNA maturation or RNA proofreading, providing a mechanism by which helicase activity alters the activation state of target RNAs through regulation of the reaction equilibrium