Deletion analysis of the polyadenylation signal of a pea ribulose-1,5-bisphosphate carboxylase small-subunit gene.

The polyadenylation signal of a pea gene for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcS) has been analyzed by deletion mutagenesis and Ti plasmid-mediated gene transfer. Sequences between 6 and 137 bases upstream from the normal polyadenylation sites in this gene (bases -6 to -137) are required for functioning of these sites. In addition, bases -111 to -235 can affect 3' end formation by altering the pattern of 3' termini seen in various transcription units. Sequences between 37 and 95 bases upstream from a cryptic polyadenylation site in this gene [A. G. Hunt, DNA 7: 329-336 (1988)] are necessary for mRNA 3' end formation at this site. At least two different parts of the 3' region of this rbcS gene can serve as a downstream element for polyadenylation at the normal poly(A) addition sites in this gene. Our studies indicate that: 1. the upstream sequences required for polyadenylation in plants are different from those defined in mammalian RNA polymerase II transcription units; 2. sequences 100 or more bases upstream and downstream from poly(A) addition sites in this gene can affect poly(A) addition site choice; and 3. there are apparently redundant downstream elements for polyadenylation in this gene.