Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health & Science University, Portland, Oregon, USA.
Department of Chemistry, Portland State University, Portland, Oregon, USA.
J Biol Chem. 2022 Feb;298(2):101552. doi: 10.1016/j.jbc.2021.101552. Epub 2021 Dec 30.
Alpha-synuclein (aSyn) is a vertebrate protein, normally found within the presynaptic nerve terminal and nucleus, which is known to form somatic and neuritic aggregates in certain neurodegenerative diseases. Disease-associated aggregates of aSyn are heavily phosphorylated at serine-129 (pSyn), while normal aSyn protein is not. Within the nucleus, aSyn can directly bind DNA, but the mechanism of binding and the potential modulatory roles of phosphorylation are poorly understood. Here we demonstrate using a combination of electrophoretic mobility shift assay and atomic force microscopy approaches that both aSyn and pSyn can bind DNA within the major groove, in a DNA length-dependent manner and with little specificity for DNA sequence. Our data are consistent with a model in which multiple aSyn molecules bind a single 300 base pair (bp) DNA molecule in such a way that stabilizes the DNA in a bent conformation. We propose that serine-129 phosphorylation decreases the ability of aSyn to both bind and bend DNA, as aSyn binds 304 bp circular DNA forced into a bent shape, but pSyn does not. Two aSyn paralogs, beta- and gamma-synuclein, also interact with DNA differently than aSyn, and do not stabilize similar DNA conformations. Our work suggests that reductions in aSyn's ability to bind and bend DNA induced by serine-129 phosphorylation may be important for modulating aSyn's known roles in DNA metabolism, including the regulation of transcription and DNA repair.
α-突触核蛋白（aSyn）是一种脊椎动物蛋白，正常情况下存在于突触前神经末梢和细胞核内，已知在某些神经退行性疾病中会形成体细胞和神经突聚集物。与疾病相关的 aSyn 聚集物在丝氨酸-129（pSyn）处高度磷酸化，而正常的 aSyn 蛋白则不然。在细胞核内，aSyn 可以直接与 DNA 结合，但结合的机制以及磷酸化的潜在调节作用还知之甚少。在这里，我们使用电泳迁移率变动分析和原子力显微镜方法的组合证明，aSyn 和 pSyn 都可以在 DNA 的大沟内结合 DNA，这是一种依赖于 DNA 长度的方式，并且对 DNA 序列没有特异性。我们的数据与这样一种模型一致，即多个 aSyn 分子以一种方式结合单个 300 个碱基对（bp）的 DNA 分子，从而使 DNA 稳定在弯曲构象中。我们提出，丝氨酸-129 磷酸化降低了 aSyn 结合和弯曲 DNA 的能力，因为 aSyn 结合 304bp 圆形 DNA 并使其强制弯曲，但 pSyn 则不能。两种 aSyn 同源物，β-和γ-突触核蛋白，与 DNA 的相互作用也与 aSyn 不同，并且不会稳定类似的 DNA 构象。我们的工作表明，丝氨酸-129 磷酸化导致 aSyn 结合和弯曲 DNA 的能力降低，可能对调节 aSyn 在 DNA 代谢中的已知作用很重要，包括转录和 DNA 修复的调节。
