Poster abstracts

Poster number 43 submitted by Abigael Muchenditsi

Effect of tetraloop stability on the affinity of tRNA for T box antiterminator

Abigael M. Muchenditsi (Department of Chemistry and Biochemistry, Ohio University), Dr. Jennifer V. Hines (Department of Chemistry and Biochemistry, Ohio University)

Abstract:
The T box transcription antitermination mechanism involves a unique RNA/RNA interaction between uncharged cognate tRNA and the 5′ mRNA leader region of T box genes. One of the interactions is between the anticodon loop of the tRNA and a specifier sequence in the mRNA. The second interaction is between the acceptor end of the tRNA and the four nucleotides of a highly conserved mRNA structural element, known as the antiterminator. The formation of this second interaction prevents the formation of an alternative terminator structural element , thus leading to transcription antitermination and full synthesis of the gene. In a model antiterminator RNA a non-conserved loop in the antiterminator was replaced by the highly stable UUCG tetraloop. Similarly, a microhelix model tRNA was closed by the UUCG tetraloop. Binding and structural studies of the resulting antiterminator-microhelix complex indicated that the helices closed by the UUCG tetraloop are perturbed in, different manners, from standard A-form geometry. In order to determine if this deformation is functionally relevant and whether tRNA affinities are affected by the loop stabillity, a series of alternative loops were investigated in fluorescence-based tRNA binding assays.

Keywords: Transccription antitermination, fluorescence, tetraloop