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Molecular and Cellular Biology, July 2001, p. 4441-4452, Vol. 21, No. 14
UMR 146 CNRS-Institut Curie, Centre
Universitaire, 91405 Orsay cedex, France
Received 6 November 2000/Returned for modification 5 January
2001/Accepted 21 April 2001
We previously described the identification of quail MafA, a novel
transcription factor of the Maf bZIP (basic region leucine zipper)
family, expressed in the differentiating neuroretina (NR). In the
present study, we provide the first evidence that MafA is
phosphorylated and that its biological properties strongly rely upon
phosphorylation of serines 14 and 65, two residues located in the
transcriptional activating domain within a consensus for phosphorylation by mitogen-activated protein kinases and which are
conserved among Maf proteins. These residues are phosphorylated by ERK2
but not by p38, JNK, and ERK5 in vitro. However, the contribution of
the MEK/ERK pathway to MafA phosphorylation in vivo appears to be
moderate, implicating another kinase. The integrity of serine 14 and
serine 65 residues is required for transcriptional activity, since
their mutation into alanine severely impairs MafA capacity to activate
transcription. Furthermore, we show that the MafA S14A/S65A mutant
displays reduced capacity to induce expression of QR1, an
NR-specific target of Maf proteins. Likewise, the integrity of serines
14 and 65 is essential for the MafA ability to stimulate expression of
crystallin genes in NR cells and to induce NR-to-lens transdifferentiation. Thus, the MafA capacity to induce differentiation programs is dependent on its phosphorylation.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.14.4441-4452.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Phosphorylation of MafA Is Essential for Its
Transcriptional and Biological Properties
*
Corresponding author. Mailing address: UMR 146 CNRS-Institut Curie, Bâtiment 110, Centre Universitaire, 91405 Orsay cedex, France. Phone: 33 1 69 86 30 73. Fax: 33 1 69 07 45 25. E-mail: Marie-Paule.Felder{at}curie.u-psud.fr.
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