A quorum sensing response in organism X results in upregulation of one gene ( qs
ID: 3166326 • Letter: A
Question
A quorum sensing response in organism X results in upregulation of one gene (qsg1) and downregulation of another (qsg2). Assume that preliminary experiments have shown that homoserine lactone functions as the autoinducer for this response. You are interested in how quorum sensing is regulated in this organism and you have isolated a mutant strain that is no longer able to upregulate qsg1 and downregulate qsg2 when treated with homoserine lactone. You find that this mutant strain fails to produce a single protein that is present in the wildtype strain due to a frameshift mutation within a particular gene (qsg3). Based on the various mechanisms of gene regulation discussed in class, propose a mechanism for how qsg1 and qsg2 expression is regulated. Describe at the molecular level all elements and allosteric interactions that your proposed mechanism requires.. There is not a unique answer to this question; multiple combinations of repressors and/or activators and/or small RNAs etc can be invoked. Your answer should be detailed but concise
Explanation / Answer
Upregulation usually means the product or protein is expressed more and down regulation means its under expressed,compared to the wild type (as reference). Down regulation is a sort of negative mechanism.Here homoserine lactone acts as an inducer, where in the presence of the inducer, the gene qsg1 is transcribed, as the transcription factors( activators) bind to the DNA binding site and helps RNA polymerase bind to the promoter region.
In the absence of the inducer, the repressor binds to the operator and reduces transcription, so down regulation of qsg2 gene takes place. The protein will be less produced. Due to frame-shift mutation, the RNA polymerase enzyme cannot bind to the promoter region due to a stop codon being rendered or the transcription process may break and the complete protein cannot be produced.