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The CoMed™ system

A plethora of yeast-based expression platform exists and a range of these platforms can be offered by Pharmedartis, preferentially the methylotrophic yeast Hansenula polymorpha and the dimorphic yeast Arxula adeninivorans. All of them have particular favourable characteristics and advantages in specific product and process developments. However all have drawbacks and limitations. Sometimes attempts to produce a recombinant protein fail completely. In other cases, productivity, secretion or modification and processing are severely impaired, thereby preventing the development of a competitive production process or a marketable product. It is evident that no single system is optimal for all proteins. Hence, predictions for a successful strain and process development can only be made to a certain extent, and misjudgement cannot be excluded. This in turn means that an initial selection may result in costly time- and resource-consuming failures. It is therefore desirable if one can assess several selected organisms in parallel for criteria such as secretion or appropriate protein processing in a given case. This can be achieved by a vector or vector system that can be targeted to the various platform candidates. As such the CoMed® system has been deve

Which elements are needed for a wide-range expression vector?

The design of a vector suited for a wide range of fungal organisms must contain both a targeting element and a selection marker suitable for all test species. The promoter that drives heterologous gene expression must be functional in all these organisms. Some A. adeninivorans and H. polymorpha fulfil these criteria. For selection, the A. adeninivorans-derived LEU2 or ALIV1 genes can be employed. The conserved rDNA is an obvious universal target for integration. The design of the basic vector is depicted in the following figure.

 

Available strains, vectors and components of the CoMed® system (selection)

Strains

Designation

phenotype

characteristics

Arxula adeninivorans

MedAa1

wild type

robust established strain isogenic to LS3

MedAa2

leu

MedAa3

ilv

Hansenula polymorpha

MedHp1

ura

robust established strain isogenic to RB11 and LR9

MedHp2

leu


MedHp3

leu

strain with increased MOX- and FMD-dependent gene expression Patent protection applied

Pichia pastoris, Saccharomyces cerevisiae and Yarrowia lipolytica strains.

 

 Vector elements

Promoters

TEF1

Established strong constitutive promoter element, applied to a range of feasibility studies.

FMD

Selection marker

ALEU2

replace the undesired hygromycine selection system

AILV1

Integration elements

A. adeninivorans and H. polymorpha-derived rDNA element.