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Jackman to Present on tRNA guanylyltransferase

Professor Jane Jackman, from the Department of Chemistry and Biochemistry at Ohio State University, will visit the IUP Chemistry Department on Friday, October 7, 2011, and present a lecture on tRNA guanylyltransferase.

Dr. Jackman will visit with department faculty and students before presenting the lecture “Putting it in reverse: 3'-5' nucleotide addition catalyzed by tRNAHis guanylyltransferase enzymes” from 3:35 to 4:25 p.m. in Weyandt 240. Light refreshments will be served, and all are welcome to attend.


The tRNAHis guanylyltransferase (Thg1) is an essential enzyme in yeast that catalyzes the addition of a single indispensable G residue (G-1) to the 5'-end of tRNAHis. Addition of G-1 occurs via an unusual 3'-5' nucleotide addition reaction, in the opposite direction to nucleotide addition catalyzed by all known DNA/RNA polymerases. Nonetheless, the recent crystal structure of human Thg1 revealed unexpected structural homology between Thg1 and canonical 5'-3' DNA polymerases, suggesting that Thg1 similarly uses a two metal-ion active site for nucleotide addition. The mechanism by which Thg1 uses this well-studied active site to catalyze reverse (3'-5') nucleotide addition is currently under investigation.

Thg1 is a member of a large enzyme family with members in eukarya, where G-1 addition is universally required, but Thg1-like proteins (TLPs) have been identified in archaea, bacteria, and mitochondria, where the biological function of the enzymes is less well-understood. Using biochemical and genetic techniques, we have identified roles for TLPs in previously unknown nucleic acid 5'-end repair and editing reactions, providing evidence for novel uses for Thg1-catalyzed 3'-5' nucleotide addition reactions in biology. These activities are likely to play critical roles in maintaining a high-quality pool of cellular RNAs.

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