3'-end-forming signals of yeast mRNA.

The signals required for forming 3'-ends of mRNAs from the yeast Saccharomyces cerevisiae differ from the corresponding signals of higher eukaryotes. Yeast signals consist of three elements: (1) the efficiency element, which enhances the efficiency of downstream positioning elements; (2) the positioning element, which positions the poly(A) site; and (3) the actual poly(A) site. These three elements are not only necessary, but also sufficient for mRNA 3'-end formation in yeast.