POLI-DRIVEN INTEGRATIVE EXPRESSION VECTORS FOR YEAST

A novel expression vector for yeast has been constructed from the regu latory elements present in the polI promoter and the enhancer/terminat ion region (E/T) of rDNA. Under some conditions, this promoter/vector combination produces small RNAs such as the hammerhead RNA sequence at levels comparable to polII- and polIII-dependent systems. No stable t ranscription product can be demonstrated with this vector when the enh ancer/termination sequence is less than 100 nucleotides downstream fro m the promoter. On the other hand, high expression of a stable, hammer head RNA molecule can be obtained from this vector by inserting a 400- bp fragment containing the ADH1 transcription termination region upstr eam of the E/T. RNAs produced by this vector are polyadenylated and mu ltiple copies of this plasmid can be stably integrated into the yeast chromosome. (C) 1997 Elsevier Science B.V.