The B.t.-toxin-coding region
contains elements characteristic of plant-polyadenylation signals. A,
Schematic representation comparing the structure of typical plant and
mammalian polyadenylation signals. Sequence motifs characteristic of
the plant FUE and NUE, as well as the mammalian downstream element
(DSE), are indicated. The poly(A+) addition sites are
represented by arrows. Plants can use multiple poly(A+)
addition sites downstream of specific NUEs within a transcript. The
cleavage of a plant transcript usually occurs at a Py/A dinucleotide
(YA). Mammalian transcripts are usually cleaved at a single site
corresponding to a C/A dinucleotide (CA). B, Identification of elements
characteristic of plant polyadenylation signals upstream of the
poly(A+) addition sites in the
B.t.-toxin-coding region. The putative plant
polyadenylation signals in segments 2, 3, and 4 of the
B.t.-toxin-coding region were compared with the most
commonly used polyadenylation sites in the rbcS-E9 and
octopine synthase (OCS) genes. The positions of the FUE
and NUE relative to the cleavage site (CS) are indicated.