Charles Morán - Academia.edu (original) (raw)

Papers by Charles Morán

Nucleic Acids Research, 1981

We report the nucleotide sequence of the promoter for a Bacillus subtilis gene (spoVC) whose tran... more We report the nucleotide sequence of the promoter for a Bacillus subtilis gene (spoVC) whose transcription is controlled by a 37,000 dalton species of B. subtilis sigma factor known as sigma 37 but not by the principal- sigma factor of 55,000 daltons (sigma 55). Using S1 nuclease mapping we show that the startpoint for sigma 37-directed transcription of the spoVC gene in vitro corresponded closely to the 5' terminus of in vivo synthesized spoVC RNA. The binding site for sigma 37-containing RNA polymerase extended from 43 bp to 51 bp (positions -43 to -51) upstream from the transcription startpoint to 22 bp (position +22) downstream from the startpoint. The nucleotide sequence of the spoVC promoter differed significantly from promoters whose recognition is controlled by sigma 55 but was similar to other sigma 37- controlled promoters in regions known to be important in promoter recognition. Our results are consistent with the hypothesis (Lee and Pero, J. Mol. Biol., in press) that sigma factors work by contacting specific bases in both the -35 and -10 regions of promoters.

Bacterial endospores are encased in a complex protein coat, which confers protection against noxi... more Bacterial endospores are encased in a complex protein coat, which confers protection against noxious chemicals and influences the germination response. In Bacillus subtilis, over 20 polypeptides are organized into an amorphous undercoat, a lamellar lightly staining inner structure, and an electron-dense outer coat. Here we report on the identification of a polypeptide of about 30 kDa required for proper coat assembly, which was extracted from spores of a gerE mutant. The N-terminal sequence of this polypeptide matched the deduced product of the tasA gene, after removal of a putative 27-residue signal peptide, and TasA was immunologically detected in material extracted from purified spores. Remarkably, deletion of tasA results in the production of asymmetric spores that accumulate misassembled material in one pole and have a greatly expanded undercoat and an altered outer coat structure. Moreover, we found that tasA and gerE mutations act synergistically to decrease the efficiency of spore germination. We show that tasA is the most distal member of a three-gene operon, which also encodes the type I signal peptidase SipW. Expression of the tasA operon is enhanced 2 h after the onset of sporulation, under the control of H . When tasA transcription is uncoupled from sipW expression, a presumptive TasA precursor accumulates, suggesting that its maturation depends on SipW. Mature TasA is found in supernatants of sporulating cultures and intracellularly from 2 h of sporulation onward. We suggest that, at an early stage of sporulation, TasA is secreted to the septal compartment. Later, after engulfment of the prespore by the mother cell, TasA acts from the septal-proximal pole of the spore membranes to nucleate the organization of the undercoat region. TasA is the first example of a polypeptide involved in coat assembly whose production is not mother cell specific but rather precedes its formation. Our results implicate secretion as a mechanism to target individual proteins to specific cellular locations during the assembly of the bacterial endospore coat.

Molecular and General Genetics, 1982

We have determined the nucleotide sequence of twoBacillus subtilis promoters (veg andtms) that ar... more We have determined the nucleotide sequence of twoBacillus subtilis promoters (veg andtms) that are utilized by the principal form ofB. subtilis RNA polymerase found in vegetative cells (σ55-RNA polymerase) and have compared our sequences to those of several previously reportedBacillus promoters. Hexanucleotide sequences centered approximately 35 (the “-35” region) and 10 (the “-10” region) base pairs upstream from theveg andtms transcription startpoints (and separated by 17 base pairs) corresponded closely to the consensus hexanucleotides (TTGACA and TATAAT) attributed toEscherichia coli promoters. Conformity to the preferred -35 and -10 sequences may not be sufficient to promote efficient utilization byB. subtilis RNA polymerase, however, since three promoters (veg, tms andE. coli tac) that conform to these sequences and that are utilized efficiently byE. coli RNA polymerase were used with highly varied efficiencies byB. subtilis RNA polymerase. We have also analyzed mRNA sequences in DNA located downstream from eightB. subtilis chromosomal and phage promoters for nucleotide sequences that might signal the initiation of translation. In accordance with the rules of McLaughlin, Murray and Rabinowitz (1981), we observe mRNA nucleotide sequences with extensive complementarity to the 3′ terminal region ofB. subtilis 16S rRNA, followed by an initiation codon and an open reading frame.

Molecular Microbiology, 1993

Endospore formation in Bacillus subtilis is a morphologically complex process in which the bacter... more Endospore formation in Bacillus subtilis is a morphologically complex process in which the bacterium divides into two compartments (forespore and mother cell) that follow different developmental paths. Compartment-specific transcription in the forespore is initiated by RNA polymerase containing σ;F, and results in the forespore-specific production of σ;G, which directs most of the subsequent forespore-specific transcription. The activity of σ;F is thought to be restricted to the forespore by the sigma factor antagonist SpollAB. We used antibodies against SpollAB to monitor its accumulation during sporulation. We found that SpollAB accumulates early after the initiation of sporulation, and that it was present in the mother-cell compartment 2h after σ;F became active in the forespore. SpollAB disappeared preferentially from the forespore during development, and its disappearance from the forespore compartment correlated with the activation of σ;G in that compartment, raising the possibility that SpollAB may be involved regulating σ;G activity. We tested whether SpollAB could antagonize σ;G activity by replacing the σ;F-dependent promoter that drives expression of spolllG, the structural gene for σ;G, with a σ;H-dependent promoter. This resulted in a lytic phenotype that was supressed by the simultaneous expression of a plasmid-borne copy of spollAB. This suggests that SpollAB can suppress this effect of σ;G expression. Moreover, these cells formed spores efficiently. Since σ;G synthesis in these cells was not restricted to the forespore by the σ;F-dependent transcription of its structural gene that normally occurs in wild-type cells, the forespore-specific activity of σ;G required for Sporulation appears to have resulted from expression of SpollAB.

Molecular Microbiology, 2001

The important human pathogen Streptococcus pyogenes (the group A streptococcus or GAS) causes dis... more The important human pathogen Streptococcus pyogenes (the group A streptococcus or GAS) causes diseases ranging from mild, self-limiting pharyngitis to severe invasive infections. Regulation of the expression of GAS genes in response to specific environmental differences within the host is probably key in determining the course of the infectious process, however, little is known of global regulators of gene expression in GAS. Although secondary RNA polymerase sigma factors act as global regulators of gene expression in many other bacteria, none has yet been isolated from the GAS. The newly available GAS genome sequence indicates that the only candidate secondary sigma factor is encoded by two identical open reading frames (ORFS). These ORFS encode a protein that is 40% identical to the transcription factor ComX, believed to act as an RNA polymerase sigma factor in Streptococcus pneumoniae. To test whether the GAS ComX homologue functions as a sigma factor, we cloned and purified it from Escherichia coli. We found that in vitro, this GAS protein, which we call s X , directed core RNA polymerase from Bacillus subtilis to transcribe from two GAS promoters that contain the cin-box region, required for transcription by S. pneumoniae ComX in vivo. On the other hand, GAS s X did not promote transcription of a GAS promoter (hasA ) expected to be dependent on s A , the housekeeping or primary RNA polymerase sigma factor. Addition of monoclonal antibody that inhibited s A -directed transcription had no effect on s X -directed transcription, showing that the latter was not the result of contaminating s A . Transcription of both cinbox-containing promoters initiated downstream of the cin-box and two different single basepair substitutions in the cin-box of the cinA promoter each caused a severe reduction of s X -directed transcription in vitro. Thus, the cin-box is required for s X -directed transcription.

Bulletin of Volcanology, 2000

Mount Rainier is one of the most seismically active volcanoes in the Cascade Range, with an aver... more Mount Rainier is one of the most seismically active volcanoes in the Cascade Range, with an average of one to two high-frequency volcano-tectonic (or VT) earthquakes occurring directly beneath the summit in a given month. Despite this level of seismicity, little is known about its cause. The VT earthquakes occur at a steady rate in several clusters below the inferred base of the Quaternary volcanic edifice. More than half of 18 focal mechanisms determined for these events are normal, and most stress axes deviate significantly from the regional stress field. We argue that these characteristics are most consistent with earthquakes in response to processes associated with circulation of fluids and magmatic gases within and below the base of the edifice.Circulation of these fluids and gases has weakened rock and reduced effective stress to the point that gravity-induced brittle fracture, due to the weight of the overlying edifice, can occur. Results from seismic tomography and rock, water, and gas geochemistry studies support this interpretation. We combine constraints from these studies into a model for the magmatic system that includes a large volume of hot rock (temperatures greater than the brittle–ductile transition) with small pockets of melt and/or hot fluids at depths of 8–18 km below the summit. We infer that fluids and heat from this volume reach the edifice via a narrow conduit, resulting in fumarolic activity at the summit, hydrothermal alteration of the edifice, and seismicity.

Journal of Geophysical Research, 1994

Several changes have occurred in seismicity associated with Mount St. Helens since it last erupte... more Several changes have occurred in seismicity associated with Mount St. Helens since it last erupted in October 1986. Perhaps the most significant is the recurrence of earthquakes deeper than 3 km, previously observed only in the months following the cataclysmic eruption of May 18, 1980, and briefly in March 1982. Events located below 6.5 km define a circular aseismic zone, similar in location to one observed after May 18, 1980. Focal mechanisms are computed for two depth ranges, 4-6.5 km (Intermediate) and 6.5-10 km (Deep), using both polarity and amplitude ratio data. Mechanisms for Intermediate events are mostly strike-slip, and many P and T axes point in directions --80 ø offset from the regional stress field, indicating that earthquakes in this zone are caused by magmatic as well as tectonic forces. Mechanisms for Deep events are also mostly strike-slip, and P and T axes form a pattern suggestive of a pressure increase within the aseismic zone. The observed Deep patterns are compared with theoretical stress fields generated by a numerical model of a pressurized hole in an elastic plate. Results from modeling support the pressure increase hypothesis for 1987-1992 seismicity, in contrast to a pressure drop for post-May 18, 1980, earthquakes. This apparent repressurization is proposed to be a result of the sealing of the shallow conduit system. SEISMICITY AT MOUNT ST. I-IELEN$ 4345 ©© ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß © © .... © © © © © © ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß 90% Confidence limit Pressure Inside Cylinder, bars Figure 6. (continued) 4348 MORAN: SEISMICITY AT MOUNT ST. HELENS 122.21 46.22 tN 26 b ß 58 4o o o øO 12KM 46.19 122.17 c ß eee eeeeeeeeeeeeeeeeeee ß •e e ß ß ß ß ee = ß ee ß . ß • S• * .

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2008

In response to NASA's announced requirement for Earth hazard monitoring sensor-web technology, a ... more In response to NASA's announced requirement for Earth hazard monitoring sensor-web technology, a multidisciplinary team involving sensor-network experts (Washington State University), space scientists (JPL), and Earth scientists (USGS Cascade Volcano Observatory (CVO)), is developing a prototype dynamic and scaleable hazard monitoring sensor-web and applying it to volcano monitoring. The combined Optimized Autonomous Space -In-situ Sensor-web (OASIS) will have two-way communication capability between ground and space assets, use both space and ground data for optimal allocation of limited power and bandwidth resources on the ground, and use smart management of competing demands for limited space assets. It will also enable scalability and seamless infusion of future space and in-situ assets into the sensorweb. 12 1 1-4244-1488-1/08/$25.00 ©2008 IEEE 2 IEEEAC paper #1144, Version 2, Updated October 24, 2007 mission needs and local bandwidth information in real-time; and 4) remote network management and reprogramming tools. The space and in-situ control components of the system will be integrated such that each element is capable of autonomously tasking the other. Sensor-web data acquisition and dissemination will be accomplished through the use of the Open Geospatial Consortium Sensorweb Enablement protocols. The three-year project will demonstrate end-to-end system performance with the in-situ test-bed at Mount St. Helens and NASA's EO-1 platform.

Bulletin of Volcanology, 2002

Shishaldin Volcano, in the central Aleutian volcanic arc, became seismically restless during the ... more Shishaldin Volcano, in the central Aleutian volcanic arc, became seismically restless during the summer of 1998. Increasing unrest was monitored using a newly installed seismic network, weather satellites, and rare local visual observations. The unrest culminated in large eruptions on 19 April and 22–23 April 1999. The opening phase of the 19 April eruption produced a sub-Plinian column that rose to 16 km before rapidly dissipating. About 80 min into the 19 April event we infer that the eruption style transitioned to vigorous Strombolian fountaining. Exceptionally vigorous seismic tremor heralded the 23 April eruption, which produced a large thermal anomaly observable by satellite, but only a modest, 6-km-high plume. There are no ground-based visual observations of this eruption; however we infer that there was renewed, vigorous Strombolian fountaining. Smaller low-level ash-rich plumes were produced through the end of May 1999. The lava that erupted was evolved basalt with about 49% SiO2. Subsequent field investigations have been unable to find a distinction between deposits from each of the two major eruptive episodes.