REPLICATION-INDEPENDENT CIS-ACTING ELEMENT OF A MAIZE HISTONE GENE PROMOTER

A chimeric gene containing the beta-glucuronidase (GUS) coding sequence fused to the maize histone H4C7 gene promoter was expressed in transient assays in tobacco mesophyll protoplasts revealing the replication-independent activity of the plant histone gene promoter. Functional analysis of 5' deletions of the H4C7 promoter suggested the presence of antagonistic activities in a region encompassing the plant histone-specific octamer and a hybrid hexameric motif, and revealed an essential cis-acting positive element between nucleotides -82 and -36 relative to the TATA box. Furthermore, point mutations introduced in the CCATCGAAC motif present in this region drastically reduced the activity of the H4C7 promoter. We conclude this nonameric sequence, present in the 5' flanking DNA sequence of most plant histone genes, to be a positive cis-acting element controlling the basal replication-independent activity of the H4C7 promoter.