The sequence of a nearly unclonable 22.8 kb segment on the left arm chromosome VII from Saccharomyces cerevisiae reveals ARO2, RPL9A, TIP1, MRF1 genes and six new open reading frames.

The nucleotide sequence of 22,803 bp on the left arm of chromosome VII was determined by polymerase chain reaction-based approaches to compensate for the unstable character of cosmid clones from this region of the chromosome. The coding density of the sequence is particularly high (more than 83%). Twelve open reading frames (ORFs) longer than 300 bp were found, two of which (at the left side) have been described previously (James et al., 1995) after sequencing of an overlapping cosmid. Four other ORFs correspond to published sequences of the known genes ARO2, RPL9A, TIP1 and MRF1. ARO2 codes for chorismate synthetase. RPL9A for protein L9 of the large ribosomal subunit and MRF1 for a mitochondrial translation release factor. The TIP1 product interacts with Sec20p and is thus involved in transport from endoplasmic reticulum to Golgi. Five of the remaining ORFs have not been identified previously, while the sixth (YGL142c) has been partially sequenced as it lies 5' upstream of MRF1. These six ORFs are relatively large (between 933 and 3657 nucleotides). YGL146c, YGL142c, YGL140c and YGL139w have no significant homology to any protein sequence presently available in the public databases, but show two, nine, nine and eight putative transmembrane spans, respectively. YGL144c has a serine active site signature of lipases. YGL141w has limited homology to several human proteins, one of which mediates complex formation between papillomavirus E6 oncoprotein and tumor suppressor protein p53.