A hybrid yeast promoter comprising constituents of the 5' non-coding PGK region and, as an upstream activation sequence, the upstream activation sequence of the GAL10 gene of Saccharomyces cerevisiae, and which does not contain the endogenous PGK upstream activation sequence. Preferably the GAL10 upstream activation sequence is provided at a site from which the PGK upstream activation sequence has been deleted. The hybrid promoter confers galactose regulation of gene transcription.
