TY  - JOUR
A1  - Rico, Sergio
A1  - Yepes, Ana
A1  - Rodriguez, Hector
A1  - Santamaria, Jorge
A1  - Antoraz, Sergio
A1  - Krause, Eva M.
A1  - Diaz, Margarita
A1  - Santamaria, Ramon I.
T1  - Regulation of the AbrA1/A2 Two-Component System in Streptomyces coelicolor and the Potential of Its Deletion Strain as a Heterologous Host for Antibiotic Production
JF  - PLOS ONE
N2  - The Two-Component System (TCS) AbrA1/A2 from Streptomyces coelicolor M145 is a negative regulator of antibiotic production and morphological differentiation. In this work we show that it is able to auto-regulate its expression, exerting a positive induction of its own operon promoter, and that its activation is dependent on the presence of iron. The overexpression of the abrA2 response regulator (RR) gene in the mutant DabrA1/A2 results in a toxic phenotype. The reason is an excess of phosphorylated AbrA2, as shown by phosphoablative and phosphomimetic AbrA2 mutants. Therefore, non-cognate histidine kinases (HKs) or small phospho-donors may be responsible for AbrA2 phosphorylation in vivo. The results suggest that in the parent strain S. coelicolor M145 the correct amount of phosphorylated AbrA2 is adjusted through the phosphorylation-dephosphorylation activity rate of the HK AbrA1. Furthermore, the ABC transporter system, which is part of the four-gene operon comprising AbrA1/A2, is necessary to de-repress antibiotic production in the TCS null mutant. Finally, in order to test the possible biotechnological applications of the DabrA1/A2 strain, we demonstrate that the production of the antitumoral antibiotic oviedomycin is duplicated in this strain as compared with the production obtained in the wild type, showing that this strain is a good host for heterologous antibiotic production. Thus, this genetically modified strain could be interesting for the biotechnology industry.
KW  - signal-transduction systems
KW  - biosynthetic gene-cluster
KW  - escherichia coli
KW  - response regulator
KW  - oviedomycin
KW  - expression
KW  - organization
KW  - integration
KW  - bacteria
KW  - sequence
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-115151
SN  - 1932-6203
VL  - 9
IS  - 10
ER  - 
TY  - JOUR
A1  - Volceanov, Larisa
A1  - Herbst, Katharina
A1  - Biniossek, Martin
A1  - Schilling, Oliver
A1  - Haller, Dirk
A1  - Nölke, Thilo
A1  - Subbarayal, Prema
A1  - Rudel, Thomas
A1  - Zieger, Barbara
A1  - Häcker, Georg
T1  - Septins Arrange F-Actin-Containing Fibers on the Chlamydia trachomatis Inclusion and Are Required for Normal Release of the Inclusion by Extrusion
JF  - MBIO
N2  - Chlamydia trachomatis is an obligate intracellular human pathogen that grows inside a membranous, cytosolic vacuole termed an inclusion. Septins are a group of 13 GTP-binding proteins that assemble into oligomeric complexes and that can form higher-order filaments. We report here that the septins SEPT2, -9, -11, and probably -7 form fibrillar structures around the chlamydial inclusion. Colocalization studies suggest that these septins combine with F actin into fibers that encase the inclusion. Targeting the expression of individual septins by RNA interference (RNAi) prevented the formation of septin fibers as well as the recruitment of actin to the inclusion. At the end of the developmental cycle of C. trachomatis, newly formed, infectious elementary bodies are released, and this release occurs at least in part through the organized extrusion of intact inclusions. RNAi against SEPT9 or against the combination of SEPT2/7/9 substantially reduced the number of extrusions from a culture of infected HeLa cells. The data suggest that a higher-order structure of four septins is involved in the recruitment or stabilization of the actin coat around the chlamydial inclusion and that this actin recruitment by septins is instrumental for the coordinated egress of C. trachomatis from human cells. The organization of F actin around parasite-containing vacuoles may be a broader response mechanism of mammalian cells to the infection by intracellular, vacuole-dwelling pathogens. IMPORTANCE Chlamydia trachomatis is a frequent bacterial pathogen throughout the world, causing mostly eye and genital infections. C. trachomatis can develop only inside host cells; it multiplies inside a membranous vacuole in the cytosol, termed an inclusion. The inclusion is covered by cytoskeletal "coats" or "cages," whose organization and function are poorly understood. We here report that a relatively little-characterized group of proteins, septins, is required to organize actin fibers on the inclusion and probably through actin the release of the inclusion. Septins are a group of GTP-binding proteins that can organize into heteromeric complexes and then into large filaments. Septins have previously been found to be involved in the interaction of the cell with bacteria in the cytosol. Our observation that they also organize a reaction to bacteria living in vacuoles suggests that they have a function in the recognition of foreign compartments by a parasitized human cell.
KW  - mammalian septins
KW  - host-cells
KW  - binding
KW  - proteins
KW  - organization
KW  - cytoskeleton
KW  - cytokinesis
KW  - mechanisms
KW  - expression
KW  - protease
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-115421
SN  - 2150-7511
VL  - 5
IS  - 5
ER  -