SEQUENCE-ANALYSIS OF A 40.2-KB DNA FRAGMENT LOCATED NEAR THE LEFT TELOMERE OF YEAST CHROMOSOME-X

We have sequenced on both strands a 40,257 bp fragment located near th e left telomere of chromosome X of Saccharomyces cerevisiae. The seque nced segment contains 21 open reading frames (ORFs) at least 100 amino acids long. Five of the ORFs correspond to known amino acid sequences : two hypothetical proteins in the subtelomeric Y' repeat region of 65 .4 and 12.8 KDa, the cytochrome B pre-mRNA processing CBP1 protein, th e mitochondrial nuclease NUC1 and the CRT1 protein. Of the 16 remainin g ORFs, eight show highest homologies with the S. cerevisiae hexose tr ansporters family (two ORFs), the yeast alpha-glucosidase (two ORFs), the yeast PEP1 precursor, the Escherichia coli galactoside O-acetyltra nsferase, the S. cerevisiae 137.7 KDa protein located in the Y' region and a protein of unknown function of Schizosaccharomyces pombe. Final ly, eight of the ORFs exhibit no significant similarity with any amino acid sequences described in data banks. DNA sequence comparison has r evealed the presence of different repeated elements characteristic of yeast chromosome ends. Disruption studies have been performed on two O RFs encoding putative proteins of unknown function. The sequence has b een entered in the EMBL Data Library under Accession Number Z34098.