THE CONFORMATION OF TRANSFER-RNA GENES - CHEMICAL MODIFICATION STUDIES

It has been suggested that eukaryotic tRNA genes might adopt a higher order stem and loop structure to facilitate transcription by interacti on of their variably spaced intragenic promoter blocks. Using sodium b isulphite, which reacts specifically with cytosine residues in single- stranded nucleic acids, no deamination of C in the TTCGAA sequence of the 3' ICR of a tRNA(Leu) gene could be detected under conditions whic h caused 60% deamination of cytosine residues within the loop region o f a synthetic cruciform cloned in the same negatively supercoiled plas mid vector. We conclude that, under these conditions, such structures occur in tRNA genes very rarely, if at all.