NARROW A T-RICH ZONES PRESENT AT THE DISTAL 5'-FLANKING SEQUENCES OF THE ZEIN GENES ZC1 AND ZC2 BIND A UNIQUE 30-KDA HMG-LIKE PROTEIN/

Nuclear extracts from maize endosperm were used to investigate protein -DNA interactions in the 5'-upstream region of the Zc1 and Zc2 genes. These genes encode for zeins of apparent molecular mass (MW(app)) 16 a nd 28 kDa, respectively, which accumulate in the endosperm during seed maturation. Binding assays revealed specific binding of a nuclear pro tein to three A/T-rich elements, 0.9-1.0 kbp upstream from the initiat ion codon. One of these elements (41 bp, 88 % A/T), present in Zc1, co ntained a 13 nucleotide duplication. The other two (28 bp, 86% A/T; 42 bp alternating A-T) are consecutive elements in Zc2. Competition expe riments strongly suggest that the three elements bind to the same prot ein. Protein-DNA interaction was detected in endosperm nuclear extract s of 8 to 21 days after pollination (DAP), as well as in 25 DAP embryo s and in different tissues from plantlets. The protein factor has an M W(app) of ca. 30 kDa. This factor has properties suggesting it is an H MG-like protein. These results are consistent with a growing accumulat ion of data for a number of genes indicating that A/T-rich elements, l ocated at distal and proximal zones of the 5'-flanking sequences, inte ract with HMG-like proteins.