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Recent discoveries in the area of ribonucleic acids (RNAs) have expanded the biological roles of RNA molecules. In addition to playing a passive template role in protein synthesis, some non-coding bacterial RNAs were recently discovered to participate in genetic regulation. Here, we study a new type of RNA-mediated genetic regulation mechanism in Bacillus subtilis. This mechanism employs the structured 5’ untranslated region of bacterial mRNA (called riboswitch) to regulate gene expression in response to small molecules (ligands), such as guanine in this case, inside the cell. Upon binding to the guanine molecule, the riboswitch, adopting a 3D structure, changes its conformation and results in downstream transcription termination. The fact that riboswitches can directly respond to small molecules and are mostly found in prokaryotes makes them potential targets for antibacterial agents. Previous studies have successfully shown that modifications of the guanine molecule at either C2 or C6 position could produce analogs that bind to the riboswitch as tightly as guanine. Some of the analogs were also able to inhibit bacterial growth. We hypothesize that modifications at both C2 and C6 positions of guanine could potentially yield analogs having a higher binding affinity to the riboswitch. As a result, we hope that these analogs could have better inhibitory effects on the bacterial genes controlled by the riboswitch. Chemicals that have modifications at both C2 and C6 positions of guanine have been synthesized in the lab. Their effects on the riboswitch-mediated genes in B. subtilis are determined using β-galactosidase assay. Our results show that two compounds synthesized in the lab have mild inhibitory effect on the riboswitch-mediated genes as well as on bacterial growth.
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Wang, Weiqing, "Gene Expression Analysis of a Guanine-Binding Riboswitch in Bacillus Subtilis" (2013). Senior Projects Spring 2013. 381.