Oncogene related sequences in fungi: linkage of some to actin

A temporally expressed gene from Schwanniomyces alluvius and detection of homologous sequences in other yeasts

The boundaries of a temporally expressed gene (EG1) located on a 6.5-kb HindIII chromosomal DNA fragment of the yeast Schwanniomyces alluvius have been defined by cDNA hybridization and S1 nuclease mapping. The sequence of this gene reveals a 474-bp open reading frame (158 aa) and a TATA-like sequence 100 bp upstream from the first start codon. The encoded protein bears little resemblance with other known yeast structural proteins, including histones. A portion of the 3' untranslated region shows 50% identity with a consensus repetitive sequence (B2) found in the mouse genome. Repetitive sequences are also located in both 5' and 3' untranslated regions. Genomic DNA analysis indicated that related sequences were detected at two loci in Schw. alluvius and one locus in Saccharomyces cerevisiae. In contrast to the continuous transcription pattern of the ADE1 genes of Schw. alluvius and S. cerevisiae, the 0.8-kb transcripts of EG1 in these yeasts were most abundant in cells in early-log phase of growth and absent in cells of late-log phase, suggesting discontinuous synthesis.

The evolutionary origin of eukaryotic transmembrane signal transduction

1. A comparison was made of transmembrane signal transduction mechanisms in different eukaryotes and prokaryotes. 2. Much attention was given to eukaryotic microbes and their signal transduction mechanisms, since these organisms are intermediate in complexity between animals, plants and bacteria. 3. Signal transduction mechanisms in eukaryotic microbes, however, do not appear to be intermediate between those in animals, plants and bacteria, but show features characteristic of the higher eukaryotes. 4. These similarities include the regulation of receptor function, adenylate cyclase activity, the presence of a phosphatidylinositol cycle and of GTP-binding regulatory proteins. 5. It is proposed that the signal transduction systems known to operate in present-day eukaryotes evolved in the earliest eukaryotic cells.