Genetically modified yeasts for the production of homogenous glycoproteins

Genetically modified yeast cells, capable of producing glycoproteins having homogeneous glycans comprising the Man5GlcNac2 structure, said yeast cells comprising the following modifications:

• a) inactivation of the Och1 gene coding for α1,6-mannosyl transferase by insertion by homologous recombination of a heterologous sequence coding for a gene of resistance to an antibiotic (delta-Och1 strain);
• b) integration by homologous recombination into an auxotrophy marker of an expression cassette comprising a promoter selected from pGAP, pGAL1, PGK, TEF, adh1, nmt 1, SV40, PMA1, CaMV, pet56 of S. cerevisiae or S. pombe, and ADH2 having the sequence SEQ ID Nos. 16-26 respectively, an open reading phase comprising the sequence coding for an α-1-2 mannosidase I comprising a targeting sequence in the endoplasmic reticulum or Golgi apparatus and a terminator of the transcription;
• and
• c) integration by homologous recombination into an auxotrophy marker of an expression cassette comprising a promoter selected from pGAP, pGAL1, PGK, TEF, adh1, nmt 1, SV40, PMA1, CaMV, pet56 of S. cerevisiae or S. pombe, and ADH2 having the sequence SEQ ID Nos. 16-26 respectively, said promoter in c) being different from the promoter in b), an open reading phase comprising the sequence coding for an exogenous glycoprotein to be produced and a terminator of the transcription,
• wherein the yeast cells are Saccharomyces cerevisiae or Schizosaccharomyces pombe.