Clustered tRNA genes in Schizosaccharomyces pombe centromeric DNA sequence repeats.

The centromere-associated B' and B DNA sequence repeats of Schizosaccharomyces pombe chromosomes I and II have been found to contain clusters of tRNA genes. The centromere II region (cen2) includes at least 22 tRNA genes distributed among five copies of the B sequence repeat containing genes specifying tRNA(Ile), tRNA(Ala), and tRNA(Val). Individual B repeats are variously associated with other tRNA genes, including those specifying tRNA(Lys), tRNA(Arg), and tRNA(Glu2). The centromere I region (cen1) contains at least six tRNA genes in two copies of the B' repeated element, including genes specifying tRNA(Ile), tRNA(Ala), and tRNA(Glu3). Multiple tandemly arranged clusters of tRNA genes are presumably conserved due to restricted recombination frequencies in the centromere regions.