Anna Magdalena as Bach's Copyist

Among the wives of eighteenth-century composers, no one is perhaps more favourably and affectionately described than Bach's second wife, Anna Magdalena (1701-1760). She has been commonly pictured as her husband's trusted assistant, copying his works in handwriting which closely resembled her husband's beautiful calligraphy. No one appreciates her contributions more than today's musicologists, for her copies are usually 'neat and accurate', and are often among the most important primary sources when Bach's autographs do not survive. Occasionally, however, it is difficult to accommodate this patronising view of her role and its significance. It is well known, for instance, that her copy of Bach's Cello Suites (BWV 1007-1012) contains an unusually large number of inaccuracies and copying errors. One must ask how many of these blunders should be ascribed to her. How would a 'neat and accurate' copyist produce such an error-ridden manuscript if she had made it from a fair copy? In this paper, I shall first discuss Anna's copies of Bach's works, and see if any particular patterns or tendencies in her copying activities emerge when these are placed in this broader chronological context. In an attempt to evaluate her performance as a copyist, I shall look at typical situations in which she worked, while at the same time seeking to discover what additional values her copies may bring to our studies of Bach's life and works.

MarA-mediated transcriptional repression of the rob promoter

The Escherichia coli transcriptional regulator MarA affects functions that include antibiotic resistance, persistence, and survival. MarA functions as an activator or repressor of transcription utilizing similar degenerate DNA sequences (marboxes) with three different binding site configurations with respect to the RNA polymerase-binding sites. We demonstrate that MarA down-regulates rob transcripts both in vivo and in vitro via a MarA-binding site within the rob promoter that is positioned between the -10 and -35 hexamers. As for the hdeA and purA promoters, which are repressed by MarA, the rob marbox is also in the "backward" orientation. Protein-DNA interactions show that SoxS and Rob, like MarA, bind the same marbox in the rob promoter. Electrophoretic mobility shift analyses with a MarA-specific antibody demonstrate that MarA and RNA polymerase form a ternary complex with the rob promoter DNA. Transcription experiments in vitro and potassium permanganate footprinting analysis show that MarA affects the RNA polymerase-mediated closed to open complex formation at the rob promoter.

The Escherichia coli transcriptional regulator MarA directly represses transcription of purA and hdeA

The Escherichia coli MarA protein mediates a response to multiple environmental stresses through the activation or repression in vivo of a large number of chromosomal genes. Transcriptional activation for a number of these genes has been shown to occur via direct interaction of MarA with a 20-bp degenerate asymmetric "marbox" sequence. It was not known whether repression by MarA was also direct. We found that purified MarA was sufficient in vitro to repress transcription of both purA and hdeA. Transcription and electrophoretic mobility shift experiments in vitro using mutant promoters suggested that the marbox involved in the repression overlapped the -35 promoter motif and was in the "backward" orientation. This organization contrasts with that of the class II promoters activated by MarA, in which the marbox also overlaps the -35 motif but is in the "forward" orientation. We conclude that MarA, a member of the AraC/XylS family, can act directly as a repressor or an activator, depending on the position and orientation of the marbox within a promoter.

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Tesis (Maestro en Ciencias con especialidad en Inmunología) UANL

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Tesis (Maestría en Ciencias, con especialidad en Microbiología Médica) U.A.N.L.

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Tesis (Maestría en Ciencias, con especialidad en Química Analítica Biomédica) U.A.N.L.