RESUMEN
DNA replication origins are fundamental to chromosome organization and duplication, but understanding of these elements is limited because only a small fraction of these sites have been identified in eukaryotic genomes. Origin Recognition Complex (ORC) and minichromosome maintenance (MCM) proteins form prereplicative complexes at origins of replication. Using these proteins as molecular landmarks for origins, we identified ORC- and MCM-bound sites throughout the yeast genome. Four hundred twenty-nine sites in the yeast genome were predicted to contain replication origins, and approximately 80% of the loci identified on chromosome X demonstrated origin function. A substantial fraction of the predicted origins are associated with repetitive DNA sequences, including subtelomeric elements (X and Y') and transposable element-associated sequences (long terminal repeats). These findings identify the global set of yeast replication origins and open avenues of investigation into the role(s) ORC and MCM proteins play in chromosomal architecture and dynamics.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Replicación del ADN , Proteínas de Unión al ADN/metabolismo , Genoma Fúngico , Origen de Réplica , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Sitios de Unión , Cromosomas Fúngicos/metabolismo , Elementos Transponibles de ADN , ADN de Hongos/biosíntesis , ADN de Hongos/genética , ADN de Hongos/metabolismo , ADN Intergénico , Componente 4 del Complejo de Mantenimiento de Minicromosoma , Componente 7 del Complejo de Mantenimiento de Minicromosoma , Proteínas Nucleares/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Complejo de Reconocimiento del Origen , ARN de Hongos/genética , ARN de Hongos/metabolismo , ARN de Transferencia/genética , ARN de Transferencia/metabolismo , Secuencias Repetitivas de Ácidos Nucleicos , Saccharomyces cerevisiae/metabolismo , Telómero/metabolismo , Secuencias Repetidas TerminalesRESUMEN
We used whole genome expression analysis to investigate the changes in the mRNA profile in cells lacking the Saccharomyces cerevisiae RNA polymerase II subunit RPB4 (Delta RPB4). Our results indicated that an essentially complete shutdown of transcription occurs upon temperature shift of this conditionally lethal mutant; 98% of mRNA transcript levels decrease at least 2-fold, 96% at least 4-fold. This data was supported by in vivo experiments that revealed a rapid and greater than 5-fold decline in steady state poly(A) RNA levels after the temperature shift. Expression of several individual genes, measured by Northern analysis, was also consistent with the whole genome expression profile. Finally we demonstrated that the loss of RNA polymerase II activity causes secondary effects on RNA polymerase I, but not RNA polymerase III, transcription. The transcription phenotype of the Delta RPB4 mutant closely mirrors that of the temperature-sensitive rpb1-1 mutant frequently implemented as a tool to inactivate the RNA polymerase II in vivo. Therefore, the Delta RPB4 mutant can be used to easily design strains that enable the study of distinct post-transcriptional cellular processes in the absence of RNA polymerase II transcription.
Asunto(s)
ARN Polimerasa II/fisiología , Transcripción Genética/fisiología , Secuencia de Bases , Cartilla de ADN , ARN Polimerasa II/genética , ARN Mensajero/genética , Proteínas de Saccharomyces cerevisiae , Eliminación de SecuenciaRESUMEN
The effect of operator experience level and root surface access on instrumentation of multirooted teeth was investigated. Fifty molars designated for extraction were randomly distributed among four operators of two different experience levels for scaling and root planing with or without surgical access. Following treatment the teeth were extracted and scored in a blind manner for residual calculus. Teeth were sectioned to allow assessment of the furcal aspects. Results show that operators of both experience levels obtained calculus-free root surfaces significantly more often with flap access than with a non-surgical approach. Additionally, operators with more experience achieved calculus-free root surfaces significantly more often than operators of lesser experience with both an open and closed procedure. However, when furcation aspects alone were assessed, it was found that the more experienced operators obtained a calculus-free surface only 68% of the time with an open approach. Results suggest that, although both surgical access and a more experienced operator significantly enhance calculus removal in molars with furcation invasion, total calculus removal in furcations utilizing conventional instrumentation may be limited.
Asunto(s)
Cálculos Dentales/terapia , Profilaxis Dental/métodos , Raspado Dental/métodos , Raíz del Diente/cirugía , Adulto , Anciano , Estudios de Evaluación como Asunto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Diente Molar , Extracción Dental , Raíz del Diente/anatomía & histologíaRESUMEN
This study was conducted to clinically compare the efficacy of freeze-dried bone allograft (FDBA) and porous hydroxylapatite granules. Nineteen pairs of intraosseous defects were grafted in seven patients. One defect of each pair was implanted with FDBA, the other with granular porous hydroxylapatite. Matching defects were treated similarly in all other aspects. Evaluations were based on both preoperative and postoperative measurements from a fixed reference point, standardized radiographs, surgical osseous measurements, and histology of degranulated tissues. Grafted sites were reentered 6 to 11 months postsurgery. Results showed a mean osseous fill of 2.1 mm for FDBA versus 1.3 mm for granular porous hydroxylapatite (P = .07). A mean clinical attachment gain of 2.2 mm for FDBA versus 1.3 mm for granular porous hydroxylapatite (P less than .05), and a mean decrease in probing depths of 3.0 mm for FDBA versus 1.4 mm for granular porous hydroxylapatite (P less than 0.5) was found. FDBA was clinically indistinguishable from host bone, whereas porous hydroxylapatite appeared to be separated from host bone by soft tissue. The data and clinical findings suggested that FDBA may have some enhanced reparative potential when compared to granular porous hydroxylapatite in the treatment of periodontal defects in humans.
Asunto(s)
Trasplante Óseo , Hidroxiapatitas , Enfermedades Periodontales/cirugía , Prótesis e Implantes , Adulto , Alveoloplastia/métodos , Durapatita , Liofilización , Humanos , Persona de Mediana Edad , Enfermedades Periodontales/patología , Bolsa Periodontal/patología , Bolsa Periodontal/cirugía , Cicatrización de HeridasRESUMEN
A single-crystal sapphire serves both as a solid microwave cavity (X band) and an anvil in a Bridgman-anvil pressure geometry. A metal gasket is used in a manner similar to its use in the diamond-anvil pressure cell, and single-crystal samples are subject to purely hydrostatic pressures. The ruby-fluorescence pressure-measurement technique is utilized. Sample size is limited to a disk approximately 0.6 mm in diameter and 0.1 mm thick. ESR data on Cr(3+) in ruby to 60 kilobars are given as an illustration of the precision and data quality. Line widths and profiles, as well as line positions, are meaningful. Very little degradation of the data is experienced at the higher pressures. The first and second derivatives of the zero-field splitting (delta) of the states in ruby with pressure are measured as ddelta/dP= (6.70+/-0.08) x 10(-4) cm(-1) kilobar(-1) and d(2)delta/dP(2)= (-2.44+/-0.30) x10(-6) cm(-1) kilobar(-2) at P=0. The gyromagnetic ratio g(11) is shown to experience a fractional change less than 2 x 10(-4) to 60 kilobars.
RESUMEN
A rapid, convenient technique for precision pressure measurement in the diamond-anvil high-pressure cell, which makes use of the sharp-line (R-line) luminescence of ruby, has been developed. The observed shift is -0.77 +/-0.03 reciprocal centimeters per kilobar for R(1) and -0.84+/- 0.03 reciprocal centimeters per kilobar for R(2) to lower energy and is approximately linear in the range studied (to 22 kilobars). Line-broadening has been observed in some instances and has been tentatively identified with nonhydrostatic conditions surrounding the ruby sample.