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An autoregulatory element of the murine Hox‐4.2 gene.

Hox‐4.2 promoter activity was assayed by transient expression assays in P19 embryonal carcinoma (EC) cells. Cotransfection of a luciferase reporter gene construct driven by Hox‐4.2 upstream sequences with an expression vector for the Hox‐4.2 gene product resulted in a 20‐fold increase in luciferase activity. This activity was specific in that the Hox‐1.6 gene product had no effect in the same assay. Mutational analysis defined a cis‐acting element with enhancer function which conferred most of this increase. Activation was largely dependent on two TAAT/ATTA motifs within this 217 bp fragment and HOX‐4.2 bound specifically to both of these motifs. The 217 bp element maps within a highly conserved region of the human Hox‐4.2 gene (HOX4B) which has been shown to display spatial enhancer activity in mice and flies. These findings suggest a conserved autoregulatory mechanism for the control of Hox‐4.2 expression.