Maf proteins represent a unique subfamily of the basic leucine-zipper (bZIP) transcription factors. Unlike other bZIP proteins that recognize short DNA binding sites (7-8 bp), Maf binds DNA sites that are 13-14 bp long. An extended recognition domain, which is unique to Maf and is located just before the bZIP region, primarily determines its DNA binding properties.

We investigated DNA bending by c-Maf using gel-mobility and DNA cyclization assays, and show that c-Maf bends DNA in a sequence-specific manner. The magnitude and direction of DNA bending were affected by changes in the binding site and by mutations known to change its DNA binding properties. In contrast, DNA bending was not affected by changes in the overall shape of the c-Maf/DNA complex. For example, identical bend magnitudes and directions were observed when the leucine-zipper of c-Maf was truncated either by two or three heptad repeats. In addition, DNA bending by c-Maf was confirmed using ligase-catalyzed cyclization assays.

This work was supported in part by the AACR-Sidney Kimmel Foundation for Cancer Research (to MD), Special Fellowship of the Leukemia & Lymphoma Society (to MD) and by Howard Hughes Medical Institute research grant to Tom Kerppola.