Compositions and methods for expression of heterologous mammalian proteins
and their secretion in the biologically active mature form using a yeast host cell
as the expression system are provided. Compositions of the invention are nucleotide
sequences encoding a signal peptide sequence for a yeast secreted protein, an optional
leader peptide sequence for a yeast secreted protein, a native propeptide leader
sequence for a mature protein of interest, and a sequence for the mature protein
of interest, all operably linked to a yeast promoter. Each of these elements is
associated with a processing site recognized in vivo by a yeast proteolytic enzyme.
Any or all of these processing sites may be a preferred processing site that has
been modified or synthetically derived for more efficient cleavage in vivo. The
compositions are useful in methods for expression of heterologous mammalian proteins
and their secretion in the biologically active mature form. Particularly, vectors
comprising these nucleotide coding sequences can be used to transform a yeast host
cell, which can then be cultured and screened for secretion of the biologically
active mature protein of interest.
