KLF15 protein is 84% identical to the rat Klf15 protein, contains 3 zinc finger motifs at its C terminus, N-terminal serine-rich stretches, and a central proline-rich segment. EMSA analysis confirmed that KLF15 and MAZ interact with the GA element of the CLCNKA promoter and showed that KLF15 binds with higher affinity and is a functional competitor of MAZ. Northern blot analysis revealed highest expression of a 2.5-kb KLF15 transcript in liver, followed by heart, skeletal muscle, and kidney. No expression was found in bone marrow or lymphoid tissues. KLF15 was also expressed in cardiac and skeletal muscle interstitial cells and in kidney inner medulla, glomeruli, and cortical interstitium. Immunofluorescence microscopy, however, demonstrated no colocalization of KLF15 with CLCNKA.