Human SIRT3 gene contains an intronic VNTR enhancer. A T > C transition occurring in the second repeat of each VNTR allele implies the presence/absence of a putative GATA binding motif. A partially overlapping AP-1 site, not affected by the transition, was also identified. Aims of the present study were: 1) to verify if GATA and AP-1 sites could bind GATA2 and c-Jun/c-Fos factors, respectively; 2) to investigate whether such sites modulate the enhancer activity of the SIRT3-VNTR alleles. DAPA assay proved that GATA2 and c-Jun/c-Fos factors are able to bind the corresponding sites. Moreover, co-transfection experiments showed that the over-expression of GATA2 and c-Jun/c-Fos factors boosts the VNTR enhancer activity in an allelic-specific way. Furthermore, we established that GATA2 and c-Jun/c-Fos act additively in modulating the SIRT3-VNTR enhancer function. Therefore, GATA2 and AP-1 are functional sites and the T > C transition of the second VNTR repeat affects their activity.

Keywords: AP-1 site, enhancer VNTR, GATA2 site, SIRT3 gene