TY  - JOUR
A1  - Grote, Jessica
A1  - Krysciak, Dagmar
A1  - Petersen, Katrin
A1  - Güllert, Simon
A1  - Schmeisser, Christel
A1  - Förstner, Konrad U.
A1  - Krishnan, Hari B.
A1  - Schwalbe, Harald
A1  - Kubatova, Nina
A1  - Streit, Wolfgang R.
T1  - The Absence of the N-acyl-homoserine-lactone Autoinducer Synthase Genes tral and ngrl Increases the Copy Number of the Symbiotic Plasmid in Sinorhizobium fredii NGR234
JF  - Frontiers in Microbiology
N2  - Plant-released flavonoids induce the transcription of symbiotic genes in rhizobia and one of the first bacterial responses is the synthesis of so called Nod factors. They are responsible for the initial root hair curling during onset of root nodule development. This signal exchange is believed to be essential for initiating the plant symbiosis with rhizobia affiliated with the Alphaproteobacteria. Here, we provide evidence that in the broad host range strain Sinorhizobium fredii NGR234 the complete lack of quorum sensing molecules results in an elevated copy number of its symbiotic plasmid (pNGR234a). This in turn triggers the expression of symbiotic genes and the production of Nod factors in the absence of plant signals. Therefore, increasing the copy number of specific plasmids could be a widespread mechanism of specialized bacterial populations to bridge gaps in signaling cascades.
KW  - Sinorhizobium fredii
KW  - plasmid copy number
KW  - plant symbioses
KW  - quorum sensing (QS)
KW  - RNA sequencing (RNA-Seq)
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-165185
VL  - 7
IS  - 1858
ER  - 
TY  - JOUR
A1  - Binas, Oliver
A1  - Bessi, Irene
A1  - Schwalbe, Harald
T1  - Structure Validation of G‐Rich RNAs in Noncoding Regions of the Human Genome
JF  - ChemBioChem
N2  - We present the rapid biophysical characterization of six previously reported putative G‐quadruplex‐forming RNAs from the 5′‐untranslated region (5′‐UTR) of silvestrol‐sensitive transcripts for investigation of their secondary structures. By NMR and CD spectroscopic analysis, we found that only a single sequence—[AGG]\(_{2}\)[CGG]\(_{2}\)C—folds into a single well‐defined G‐quadruplex structure. Sequences with longer poly‐G strands form unspecific aggregates, whereas CGG‐repeat‐containing sequences exhibit a temperature‐dependent equilibrium between a hairpin and a G‐quadruplex structure. The applied experimental strategy is fast and provides robust readout for G‐quadruplex‐forming capacities of RNA oligomers.
KW  - biophysical investigation
KW  - circular dichroism
KW  - G-quadruplexes
KW  - NMR spectroscopy
KW  - RNA
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214892
VL  - 21
IS  - 11
SP  - 1656
EP  - 1663
ER  - 
TY  - JOUR
A1  - Müller, Diana
A1  - Bessi, Irene
A1  - Richter, Christian
A1  - Schwalbe, Harald
T1  - The Folding Landscapes of Human Telomeric RNA and DNA G‐Quadruplexes are Markedly Different
JF  - Angewandte Chemie International Edition
N2  - We investigated the folding kinetics of G‐quadruplex (G4) structures by comparing the K\(^{+}\)‐induced folding of an RNA G4 derived from the human telomeric repeat‐containing RNA (TERRA25) with a sequence homologous DNA G4 (wtTel25) using CD spectroscopy and real‐time NMR spectroscopy. While DNA G4 folding is biphasic, reveals kinetic partitioning and involves kinetically favoured off‐pathway intermediates, RNA G4 folding is faster and monophasic. The differences in kinetics are correlated to the differences in the folded conformations of RNA vs. DNA G4s, in particular with regard to the conformation around the glycosidic torsion angle χ that uniformly adopts anti conformations for RNA G4s and both, syn and anti conformation for DNA G4s. Modified DNA G4s with \(^{19}\)F bound to C2′ in arabino configuration adopt exclusively anti conformations for χ. These fluoro‐modified DNA (antiTel25) reveal faster folding kinetics and monomorphic conformations similar to RNA G4s, suggesting the correlation between folding kinetics and pathways with differences in χ angle preferences in DNA and RNA, respectively.
KW  - folding landscapes
KW  - G-quadruplexes
KW  - kinetics
KW  - real-time NMR spectroscopy
KW  - TERRA RNA
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238917
VL  - 60
IS  - 19
SP  - 10895
EP  - 10901
ER  -