Different patterns of transposable elements in the vicinity of tRNA genes in yeast: a possible clue to transcriptional modulation.

We have extended the catalogue of yeast tRNA genes that are found associated with repetitive (transposable) elements. We determined the nucleotide sequences of loci containing the genes for a tRNAGln and a tRNASer2 (pY66), a tRNAGlu3 (pY80), and a tRNALys1 (pY109). Our analyses revealed that complex patterns exist in which different types of elements (Ty, delta, sigma, and tau) are involved. We could further demonstrate that in several there are alleles of which one contains a particular element and the other lacks it; such differences are also found when comparing hybridization patterns of DNA from a diploid and a haploid yeast strain. In order to investigate a possible functional role of the elements in conjunction with the tRNA genes, we compared the transcriptional activities of several tRNA genes by microinjection into Xenopus oocyte nuclei. The observed differences in expression may be attributed to the presence or absence of different elements in the vicinity of the tRNA genes.