5'-upstream cis-elements and binding factor(s) potentially involved in light-regulated expression of a Brassica napus rbcS gene.

The 5'-upstream region of a Brassica napus rbcS gene contains sequence elements that resemble the cis-regulatory elements described for other species. In band shift competition assays using whole-cell extracts and sets of deletion fragments we could assign protein binding to a region located 110-130 base pairs upstream of the transcription start site. DNase I protection experiments showed that the binding region is non-contiguous and reveals symmetry. On the non-coding strand, the sequence contains 5'-CAC-3' and 5'-GTGG-3' elements which together resemble the contiguous G-box core motif, CACGTGG, of other rbcS genes. The DNA-protein interaction was more efficient with extracts from light-grown than with those from dark-grown seedlings, indicating the possible involvement of light-regulated factors(s).