Janknecht R, Ernst W H, Houthaeve T, Nordheim A
Institute for Molecular Biology, Hannover Medical School, Germany.
Eur J Biochem. 1993 Sep 1;216(2):469-75. doi: 10.1111/j.1432-1033.1993.tb18165.x.
The serum-response factor (SRF) is essential for the induction and repression of the protooncogene c-fos. Phosphorylation of SRF has been implicated to be involved in these processes and five phosphorylation sites have already been mapped within the N-terminal region. Here we show that in vivo additional phosphorylation of SRF does occur. This modification is located primarily within amino acids 206-289, which probably contain more than one phosphorylation site. Microsequencing allowed the identification of one phosphorylation site at Ser253, which is a potential target of casein kinase II. Mutational analysis revealed that, in contrast to N-terminal phosphorylation, Ser253 phosphorylation does not affect DNA-binding properties. In addition, phosphorylation at Ser253 does not seem to change transactivation activity of SRF but rather influences its contribution to transcriptional repression. Thus, C-terminal phosphorylation of SRF may modulate c-fos basal repression.
血清反应因子（SRF）对于原癌基因c-fos的诱导和抑制至关重要。SRF的磷酸化被认为参与了这些过程，并且已经在N端区域定位了五个磷酸化位点。在这里我们表明，在体内SRF确实会发生额外的磷酸化。这种修饰主要位于氨基酸206 - 289内，该区域可能包含不止一个磷酸化位点。微量测序确定了丝氨酸253处的一个磷酸化位点，它可能是酪蛋白激酶II的潜在作用靶点。突变分析表明，与N端磷酸化不同，丝氨酸253的磷酸化不影响DNA结合特性。此外，丝氨酸253处的磷酸化似乎不会改变SRF的反式激活活性，而是影响其对转录抑制的作用。因此，SRF的C端磷酸化可能调节c-fos的基础抑制。
