The promoter region of a replication-dependent histone H3.2 gene contains a putative DNA binding site for the Jun oncoprotein within a 32-nucleotide regulatory domain. The hamster sequence differs by one nucleotide from the AP-1 consensus sequence found in several promoters responsive to phorbol 12-myristate 13-acetate. We have identified the factors interacting with this region as 42- and 45-kDa proteins by DNA affinity chromatography, immunoblotting, and UV crosslinking. These proteins, which are candidates for conferring high-level expression to the histone promoter, share an antigenic epitope with the DNA-binding domain of Jun but diverge from it at the amino terminus. The interaction of these proteins with the promoter of a replication-dependent cellular gene provides evidence that members of the Jun oncoprotein family may play specific roles in the expression of genes essential for progression of the cell cycle.