BINDING OF NICOTIANA NUCLEAR PROTEINS TO THE SUBTERMINAL REGIONS OF THE AC TRANSPOSABLE ELEMENT

Specific binding of Nicotiana nuclear protein(s) to subterminal region s of the Ac transposable element was detected using gel mobility shift assays. A sequence motif (GGTAAA) repeated in both terminal regions o f Ac, was identified as the protein binding site. Mutation of two nucl eotides in this motif was sufficient to abolish binding, Based on a se ries of competition assays, it is deduced that there is cooperative bi nding between two repeats, each similar to the GGTAAA motif, The bindi ng protein is probably similar to a previously characterized maize pro tein which binds to a GGTAAA-containing motif located in the ends of M utator. Moreover, we show that DNA from Ds1 competes for protein bindi ng to Ac termini, and we show, by sequence analysis, that GGTAAA bindi ng sites are present in the terminal region of Tgm1, Tpn1, En/Spm, Tam 3 and Ds1-like elements. This suggests that the binding protein(s) mig ht be involved in the transposition process.