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首页> 外文期刊>Molecular and Cellular Biology >Extensive mutagenesis of a transcriptional activation domain identifies single hydrophobic and acidic amino acids important for activation in vivo.
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Extensive mutagenesis of a transcriptional activation domain identifies single hydrophobic and acidic amino acids important for activation in vivo.

机译：转录激活域的广泛诱变确定了对体内激活很重要的单个疏水和酸性氨基酸。

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C1 is a transcriptional activator of genes encoding biosynthetic enzymes of the maize anthocyanin pigment pathway. C1 has an amino terminus homologous to Myb DNA-binding domains and an acidic carboxyl terminus that is a transcriptional activation domain in maize and yeast cells. To identify amino acids critical for transcriptional activation, an extensive random mutagenesis of the C1 carboxyl terminus was done. The C1 activation domain is remarkably tolerant of amino acid substitutions, as changes at 34 residues had little or no effect on transcriptional activity. These changes include introduction of helix-incompatible amino acids throughout the C1 activation domain and alteration of most single acidic amino acids, suggesting that a previously postulated amphipathic alpha-helix is not required for activation. Substitutions at two positions revealed amino acids important for transcriptional activation. Replacement of leucine 253 with a proline or glutamine resulted in approximately 10% of wild-type transcriptional activation. Leucine 253 is in a region of C1 in which several hydrophobic residues align with residues important for transcriptional activation by the herpes simplex virus VP16 protein. However, changes at all other hydrophobic residues in C1 indicate that none are critical for C1 transcriptional activation. The other important amino acid in C1 is aspartate 262, as a change to valine resulted in only 24% of wild-type transcriptional activation. Comparison of our C1 results with those from VP16 reveal substantial differences in which amino acids are required for transcriptional activation in vivo by these two acidic activation domains.
机译：C1是编码玉米花青素色素途径生物合成酶的基因的转录激活因子。 C1具有一个与Myb DNA结合域同源的氨基末端和一个酸性羧基末端，该末端是玉米和酵母细胞中的转录激活域。为了鉴定对于转录激活至关重要的氨基酸，对C1羧基末端进行了广泛的随机诱变。 C1激活域对氨基酸取代具有明显的耐受性，因为34个残基的变化对转录活性影响很小或没有影响。这些变化包括在整个C1激活域中引入不相容的螺旋氨基酸，以及大多数单个酸性氨基酸的改变，这表明激活时不需要先前假定的两亲性α-螺旋。在两个位置的取代揭示了对于转录激活重要的氨基酸。用脯氨酸或谷氨酰胺替代亮氨酸253导致大约10％的野生型转录激活。亮氨酸253在C1区域中，其中几个疏水残基与对于单纯疱疹病毒VP16蛋白的转录激活重要的残基对齐。但是，C1中所有其他疏水残基的变化表明，没有一个对于C1转录激活至关重要。 C1中的另一个重要氨基酸是天冬氨酸262，因为缬氨酸的变化仅导致24％的野生型转录激活。我们的C1结果与VP16结果的比较表明，这两个酸性激活域在体内转录激活所需的氨基酸方面存在显着差异。

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