The mod5-1 mutation is a nuclear mutation in Saccharomyces cerevisiae that reduces the biosynthesis of N6-(delta 2-isopentenyl)adenosine in both cytoplasmic and mitochondrial tRNAs to less than 1.5% of wild-type levels. The tRNA modification enzyme, delta 2-isopentenyl pyrophosphate:tRNA isopentenyl transferase, cannot be detected in vitro with extracts from mod5-1 cells. A characterization of the MOD5 gene would help to determine how the same enzyme activity in different cellular compartments can be abolished by a single nuclear mutation. To that end we have cloned the MOD5 gene and shown that it restores delta 2-isopentenyl pyrophosphate:tRNA isopentenyl transferase activity and N6-(delta 2-isopentenyl)adenosine to tRNA in both the mitochondria and the nucleus/cytoplasm compartments of mod5-1 yeast cells. That MOD5 sequences are expressed in Escherichia coli and can complement an N6-(delta 2-isopentenyl)-2-methylthioadenosine-deficient E. coli mutant leads us to conclude that MOD5 is the structural gene for delta 2-isopentenyl pyrophosphate:tRNA isopentenyl transferase.

• PMID: 3031456
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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, Non-P.H.S.

Authors

Dihanich ME, Najarian D, Clark R, Gillman EC, Martin NC, Hopper AK

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