Schuster Gadi , Professor
in our lab covers a broad range of topics unified by one theme: the
polyadenylation stimulated RNA-degradation pathway.
Through biochemistry and genetics we investigate the mechanisms of
polyadenylation and degradation of RNA and the consequences of this
system on RNA stability and gene expression. Because
polyadenylation and degradation of RNA are universal, we move back
and forth between simple and complex organisms (bacteria, Archaea,
plants and animal organelles, and human cells).
RNA degradation and polyadenylation in the chloroplast and the enzymes involved
Gene regulation at the RNA level encompasses multiple mechanisms in prokaryotes and eukaryotes, including splicing, editing, endo- and exonucleolytic cleavage, and various phenomena related to small or interfering RNAs. Ribonucleases are key players in nearly all of these post-transcriptional mechanisms, as the catalytic agents. This research focuses into the molecular mechanism of polyadenylation and RNA degradation as well as ribonuclease activities in the chloroplast, where RNase mutation or deficiency can cause metabolic defects and is often associated with plant chlorosis, embryo or seedling lethality, and/or failure to tolerate nutrient stress. Our work has focused on the exoribonuclease polynucleotide phosphorylase (PNPase), which operates in RNA maturation and degradation. We are analyzing the structure-function of an enzyme whose importance in many cellular processes in prokaryotes and eukaryotes has only begun to be uncovered. PNPase substrates are mostly generated by endonucleolytic cleavages for which the catalytic enzymes remain poorly described. Two candidate enzymes, RNase E and RNase J are under investigation in our lab. RNase E is well-described in bacteria but its function in plants is unknown: we showed it is located in the chloroplast and catalyzes endonucleolytic cleavages. RNase J was recently discovered in bacteria but like RNase E, its function in plants has yet to be explored. The parallel in vivo and in vitro analysis allows a biologically significant correlation of biochemical and in planta results for conserved and indispensable ribonucleases. Potentially, these new insights into chloroplast gene regulation will ultimately support plant improvement for agriculture.
RNA degradation and polyadenylation in human mitochondria
Mitochondria are DNA-containing organelles that function as the cell’s major providers of ATP and have been implicated in a variety of basic cellular processes, ranging from apoptosis to aging. Polyadenylation plays a critical role in controlling mRNA stability in many systems, including human mitochondria. Despite being key mechanisms which govern mitochondrial gene expression, RNA polyadenylation and turnover in human mitochondria, still remain unsolved puzzles. We have detected unstable, transient polyadenylation in human mitochondria, which is evidence of poly(A)-stimulated RNA degradation, a process known in bacteria, chloroplasts, plants mitochondria and trypanosome mitochondria and, recently, in mammalian cell nuclei. The discovery of transient polyadenylation which occurs at sites within the mitochondrial gene sequences is especially intriguing, as it is known that stable poly(A) tails decorate the mature 3’ ends of human mitochondrial mRNA.
Understanding the molecular mechanism of
mRNA degradation in human mitochondria will help to understand the
modulation of mRNA stability in this organelle. We also expect to
obtain new and important information concerning the evolution of RNA
polyadenylation, and possibly the molecular background of
mitochondrial genetic disorders related to RNA degradation.
Therefore, this information will not only be of great interest to
those studying gene expression, but also to researchers with agendas
of a medical or clinical nature.
An integrated, multidisciplinary project combining plant genetic engineering, biochemistry, chemistry and electric engineering. The key objective of this multidisciplinary project is to construct a novel, sustainable energy production system that enables the production of reducing power by a crude photosynthetic extract of a transgenic plant. The system is engineered such that the electron source (water) will be replenished continually, and the only reaction by-product – molecular oxygen and hydrogen, will be removed and collected. Therefore, this bio-energy generator will produce electricity and hydrogen, both extremely valuable resources of energy. The planned system is completely "green” in function, with absolutely no production of chemical pollutants. In collaboration with Prof. Noam Adir, Faculty of Chemistry and Prof. Avner Rothschild, Faculty of Material Science and Engineering.