Regulation of Transcription Attenuation in the B. subtilis trp Operon

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Transcription attenuation in the Bacillus subtilis trp operon is regulated by a trans-acting RNA binding protein, the product of the mtr locus. In the presence of tryptophan, Mtr recognizes, and presumably binds to, a site in the trp leader transcript. This binding influences the attenuator to form a transcription terminator. The mtr locus contains two structural genes, mtrA and mtrB; both are required to regulate the trp operon. The objective of this work is to determine how Mtr recognized its RNA target and how it influences the attenuator to cause transcription termination. Specific objectives are to: 1) purify Mtr and determine its subunit structure. 2) develop in vitro assays for Mtr function including RNA binding and transcription regulation. 3) characterize the RNA target site in the trp leader transcript and demonstrate that Mtr binds this site. Features of Mtr required for RNA-binding will also be studied. 4) determine the mechanism of tryptophan activation of Mtr. 5) determine if Mtr regulates other genes. The importance of RNA-binding proteins as gene regulators is clear. Sequence- specific RNA-protein interactions regulate a wide range of cellular processes. This work will provide information about how proteins recognize RNA and how RNA-binding proteins regulate gene expression.