Several of the complications seen in patients with both type I and type II diabetes mellitus are associated with alterations in the expression of matrix metalloproteinases. To identify the cis-acting elements that mediate the stimulatory effect of insulin on collagenase-1 (matrix metalloproteinase-1) gene transcription a series of collagenase-chloramphenicol acetyltransferase (CAT) fusion genes were transiently transfected into HeLa cells. Multiple promoter elements, including an Ets and activator protein-1 (AP-1) motif, were required for the effect of insulin. The AP-1 motif appears to be a target for insulin signaling because it is sufficient to mediate an effect of insulin on the expression of a heterologous fusion gene, whereas the data suggest that the Ets motif acts to enhance the effect of insulin mediated through the AP-1 motif. Multiple promoter elements were also required for the stimulatory effect of phorbol esters on collagenase-CAT gene transcription, and the AP-1 motif was also a target for phorbol ester signaling. However, the cis-acting elements required for the effects of insulin and phorbol esters were not identical. Moreover, phorbol esters were a much more potent inducer of collagenase-CAT gene transcription than insulin, a difference that may be explained by selective effects of insulin and phorbol esters on AP-1 expression.