The DNA-binding and transcriptional activities of MAZ, a myc-associated zinc finger protein, are regulated by casein kinase II

Myc-associated zinc finger protein (MAZ) is a transcription factor that con tains proline-rich, alanine repeats and six C2H2-type zinc finger motifs, a s well as five putative sites of phosphorylation by casein kinase II (CKII) . Site-specific mutagenesis of MAZ revealed that the serine residue at posi tion 480 was the major site of phosphorylation by CKII both in vitro and in vivo. Phosphorylation of MAZ by CKII at this serine residue was required f or maximum binding of MAZ to the pyrimidine-rich DNA of the nuclease-hypers ensitive element (NHE) in the 5'-end promoter region of the c-myc gene. Mut ation of serine at position 480 to alanine eliminated the DNA-binding activ ity of MAZ to this element. Moreover, the mutated MAZ was unable to enhance the expression of luciferase encoded by a c-myc promoter/luciferase report er gene in HeLa cells in the presence of CKII. These results suggest that p hosphorylation of the serine residue at position 480 of MAZ by CKII can con trol the function of MAZ by altering its DNA-binding activity. (C) 1999 Aca demic Press.