Phosphorylation within the MafA N terminus regulates C-terminal dimerization and DNA binding.
Phosphorylation regulates transcription factor activity by influencing dimerization, cellular localization, activation potential, and/or DNA binding. Nevertheless, precisely how this post-translation modification mediates these processes is poorly understood. Here, we examined the role of phosphorylation on the DNA-binding properties of MafA and MafB, closely related transcriptional activators of the basic-leucine zipper (b-Zip) family associated with cell differentiation and oncogenesis. Many common phosphorylation sites were identified by mass spectrometry. However, dephosphorylation only precluded the detection of MafA dimers and consequently dramatically reduced DNA-binding ability. Analysis of MafA/B chimeras revealed that sensitivity to the phosphorylation status of MafA was imparted by sequences spanning the C-terminal dimerization region (amino acids (aa) 279-359), whereas the homologous MafB region (aa 257-323) conveyed phosphorylation-independent DNA binding. Mutational analysis showed that formation of MafA dimers capable of DNA binding required phosphorylation within the distinct N-terminal transactivation domain (aa 1-72) and not the C-terminal b-Zip region. These results demonstrate a novel relationship between the phosphoamino acid-rich transactivation and b-Zip domains in controlling MafA DNA-binding activity.
Guo
Shuangli
S
From the Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
Vanderford
Nathan L
NL
Stein
Roland
R
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051473:Maf Transcription Factors, Large / Q000235:genetics / Q000378:metabolism*; D051258:MafB Transcription Factor / Q000235:genetics / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
C485159:MAFA protein, human; C490407:MAFB protein, human; D051473:Maf Transcription Factors, Large; D051258:MafB Transcription Factor; C485160:Mafa protein, mouse; C490406:Mafb protein, mouse; D011993:Recombinant Fusion Proteins; D004247:DNA