Orientation-Dependent Function of a Short CYC1 DNA Fragment in Directing mRNA 3′ End Formation in Yeast

We have cloned an 82-base-pair region spanning the site of normal 3′ end formation of Saccharomyces cerevisiae CYC1 mRNA into an integrative vector carrying the 5′ end of the actin gene (including its intron) fused in frame to HIS4ABC sequences. This vector can confer the ability to grow on histidinol if HIS4C (encoding histidinol dehydrogenase) is sufficiently expressed. With the CYC1 fragment cloned in its wild-type (forward) orientation within the actin intron, transformants cannot grow on histidinol, whereas cells transformed with the vector carrying the reverse orientation of this fragment are able to grow well. RNA transfers demonstrate that transformants containing the forward orientation accumulate