Construction of efficient centromeric, multicopy and expression vectors for the yeast Kluyveromyces marxianus using homologous elements and the promoter of a purine-cytosine-like permease.

Efficient centromeric and multicopy vectors have been constructed for the yeast Kluyveromyces marxianus using homologous ARS and centromere sequences. A homologous promoter of a purine-cytosine permease gene called PCPL3 has been cloned, using an expression system based on GUS. Its strength has been estimated in K. marxianus by putting the homologous beta-glucosidase gene under its control. This promoter is very efficient as activities higher than the ones obtained with the Saccharomyces cerevisiae PGK promoter were obtained. This promoter appears to be constitutive in various conditions tested. Its five transcription start sites have been mapped, and a derivative expression vector for K. marxianus has been constructed.