Expanding the role of FurA as essential global regulator in cyanobacteria

In the nitrogen-fixing heterocyst-forming cyanobacterium Anabaena sp. PCC 7120, the ferric uptake regulator FurA plays a global regulatory role. Failures to eliminate wild-type copies of furA gene from the polyploid genome suggest essential functions. In the present study, we developed a selectively regulated furA expression system by the replacement of furA promoter in the Anabaena sp. chromosomes with the Co2+/Zn2+ inducible coaT promoter from Synechocystis sp. PCC 6803. By removing Co2+ and Zn2+ from the medium and shutting off furA expression, we showed that FurA was absolutely required for cyanobacterial growth. RNA-seq based comparative transcriptome analyses of the furA-turning off strain and its parental wild-type in conjunction with subsequent electrophoretic mobility shift assays and semi-quantitative RT-PCR were carried out in order to identify direct transcriptional targets and unravel new biological roles of FurA. The results of such approaches led us to identify 15 novel direct iron-dependent transcriptional targets belonging to different functional categories including detoxification and defences against oxidative stress, phycobilisome degradation, chlorophyll catabolism and programmed cell death, light sensing and response, heterocyst differentiation, exopolysaccharide biosynthesis, among others. Our analyses evidence novel interactions in the complex regulatory network orchestrated by FurA in cyanobacteria

Schwannoma asintomático del nervio mediano, a propósito de un caso

El Schawannoma es un tutor benigno, encapsulado, que se origina a partir de las células de Schwann en las vainas de los nervios periféricos. Presentamos un caso de Schawannoma del nervio mediano a nivel del carpo, en una mujer de 67 años. Normalmente estos tumores se manifiestan clínicamente como una masa palpable, don color y síntomas neurológicos tales como la debilidad, parestesias o trastornos de la sensibilidad, en este caso el Schawannoma se manifestó como un tumor asintomático. El diagnóstico diferencial se realizó con un gangllión del carpo, aunque el diagnóstico definitivo lo dio el estudio histopatológico tras la resección microquirúrgica del Schawannoma. La excisión del tumor pretende preservar el nervio y mantener la integridad anatómica y funcional. Actualmente, 10 meses después del tratamiento quirúrgico, la paciente no presenta ninguna clínica.Schawannoma is a benign, encapsulated neoplasm whose origin is derived from Schwann cells of the peripheral nerve sheath. An Schawannoma of the medin nerve on the wrist of a 67 years old male, is described. These tumors usually prsent as mobile mass, pain and neurological symptoms just as weakness, parestesia or sensory disturblances; in this patient, the lesion is an asymptomatic sofá-tissue mass. Differencial diagnosis achieved with carpal ganglion, but the histological diagnosis reported Schawannoma prior microsurgical escisión. Preservation of nerve continuity and the adequate extirpation are the purposes of the therapeutical strategia. Actually, the patient are sympton-free, 10 months after the operation

FurA modulates gene expression of alr3808, a DpsA homologue in Nostoc (Anabaena) sp. PCC7120

AbstractThe DNA-binding protein from stationary phase (Dps) protein family plays an important role in protecting microorganisms from oxidative and nutritional stresses. In silico analysis of the promoter region of alr3808, a dpsA homologue from the cyanobacterium Nostoc sp. PCC7120 shows putative iron-boxes with high homology with those recognized by FurA (ferric uptake regulator). Evidence for the modulation of dpsA by FurA was obtained using in vitro and in vivo approaches. SELEX linked to PCR was used to identify PdpsA as a FurA target. Concurrently, EMSA assays showed high affinity of FurA for the dpsA promoter region. DpsA expression analysis in an insertional mutant of the alr1690-αfurA message (that exhibited an increased expression of FurA) showed a reduced synthesis of DpsA. These studies suggest that FurA plays a significant role in the regulation of the DpsA

Mesoscopic model and free energy landscape for protein-DNA binding sites: Analysis of cyanobacterial promoters

This is an open-access article distributed under the terms of the Creative Commons Attribution License.The identification of protein binding sites in promoter sequences is a key problem to understand and control regulation in biochemistry and biotechnological processes. We use a computational method to analyze promoters from a given genome. Our approach is based on a physical model at the mesoscopic level of protein-DNA interaction based on the influence of DNA local conformation on the dynamics of a general particle along the chain. Following the proposed model, the joined dynamics of the protein particle and the DNA portion of interest, only characterized by its base pair sequence, is simulated. The simulation output is analyzed by generating and analyzing the Free Energy Landscape of the system. In order to prove the capacity of prediction of our computational method we have analyzed nine promoters of Anabaena PCC 7120. We are able to identify the transcription starting site of each of the promoters as the most populated macrostate in the dynamics. The developed procedure allows also to characterize promoter macrostates in terms of thermo-statistical magnitudes (free energy and entropy), with valuable biological implications. Our results agree with independent previous experimental results. Thus, our methods appear as a powerful complementary tool for identifying protein binding sites in promoter sequences.This work was supported by the Spanish Goverment under DGICYT Projects No. FIS2011-25167, BFU2009-07424, BFU2012-31458 cofinanced by FEDER funds, Gobierno de Aragon (projects B18 and E19), “Proyecto Intramural” (BIFI) and Spanish government fellowship FPU-2012-2608 (RTR).Peer Reviewe

Iron-stress in phytoplankton determined by ELISA test

Flavodoxin and ferredoxin can be used as molecular markers for determination of biolimitation of iron in phytoplankton. Two ELISA tests have been used for determination of flavodoxin and ferredoxin respectively in samples from three endorheic lagoons

Heme binds to and inhibits the DNA-binding activity of the global regulator FurA from Anabaena sp. PCC 7120

AbstractHeme is an iron-containing cofactor that aside from serving as the active group of essential proteins is a key element in the control of many molecular and cellular processes. In prokaryotes, the family of Fur (ferric uptake regulator) proteins governs processes essential for the survival of microorganims such as the iron homeostasis. We show that purified recombinant FurA from Anabaena sp. PCC 7120 interacts strongly with heme in the micromolar range and this interaction affects the in vitro ability of FurA to bind DNA, inhibiting that process in a concentration-dependent fashion. Our results provide the first evidence of the possible involvement of heme in the regulatory function of cyanobacterial Fur