Phosphorylation of MafA is essential for its transcriptional and biological properties
Phosphorylation of MafA is essential for its transcriptional and biological properties
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DOI：
10.1128/mcb.21.14.4441-4452.2001
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发表时间：
2001-07-01
影响因子：
5.3
通讯作者：
Felder-Schmittbuhl, MP
中科院分区：
文献类型：
--
作者：
Benkhelifa, S;Provot, S;Felder-Schmittbuhl, MP
我们之前描述了鹌鹑 MafA 的鉴定，鹌鹑 MafA 是 Maf bZIP（碱性区亮氨酸拉链）家族的一种新型转录因子，在分化神经视网膜（NR）中表达。在本研究中，我们提供了第一个证据，证明 MafA 被磷酸化，并且其生物学特性强烈依赖于丝氨酸 14 和 65 的磷酸化，这两个残基位于转录激活结构域中，与丝裂原激活蛋白激酶磷酸化一致，并且在 Maf 蛋白中是保守的。这些残基在体外被 ERK2 磷酸化，但不被 p38、JNK 和 ERK5 磷酸化。然而，MEK/ERK 途径对体内 MafA 磷酸化的贡献似乎是中等的，这涉及另一种激酶。丝氨酸 14 和丝氨酸 65 残基的完整性是转录活性所必需的，因为它们突变为丙氨酸会严重损害 MafA 激活转录的能力。此外，我们发现 MafA S14A/S65A 突变体诱导 QR1 表达的能力降低，QR1 是 Maf 蛋白的 NR 特异性靶标。同样，丝氨酸 14 和 65 的完整性对于 MafA 刺激 NR 细胞中晶状体蛋白基因表达和诱导 IVR 到晶状体转分化的能力至关重要。因此，MafA 诱导分化程序的能力取决于其磷酸化。
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 IVR-to-lens transdifferentiation. Thus, the MafA capacity to induce differentiation programs is dependent on its phosphorylation.