An isolated DNA segment is disclosed which is derived from a Saccharomyces cerevisiae sorbitol dehydrogenase gene and which functions to increase expression of an associated foreign polypeptide when the DNA segment and the gene coding for the foreign polypeptide are operably linked in a vector in such a manner that the vector is replicated and carried by a host yeast cell. The functionally active portion of the segment is under the control (i) a transcriptional regulatory sequence of the sorbitol dehydrogenase gene of Saccharomyces cerevisiae, (ii) a translation initiation regulatory sequence of the sorbitol dehydrogenase gene of Saccharomyces cerevisiae, and (iii) a termination regulatory sequence of the sorbitol dehydrogenase gene of Saccharomyces cerevisiae. Yeast cells containing these regulatory sequences linked to a foreign DNA sequence are grown in medium containing sorbitol under conditions permitting a foreign polypeptide to be expressed.