Trinucleotide expansions leading to an extended poly-L-alanine segment in the poly (A) binding protein PABPN1 cause fibril formation
Trinucleotide expansions leading to an extended poly-L-alanine segment in the poly (A) binding protein PABPN1 cause fibril formation
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DOI：
10.1110/ps.03214703
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发表时间：
2003-12-01
期刊：
影响因子：
8
通讯作者：
Schwarz, E
中科院分区：
文献类型：
--
作者：
Scheuermann, T;Schulz, B;Schwarz, E
核多聚腺苷酸结合蛋白（PABPN 1）刺激多聚腺苷酸聚合酶，并在前mRNA加工过程中控制多聚腺苷酸尾的长度。野生型蛋白质在起始甲硫氨酸之后立即具有10个连续的Ala残基。编码序列中的三核苷酸扩增导致Ala延伸至总共最多17个Ala残基。携带三核苷酸扩增的个体患有眼咽肌营养不良症（OPMD）。主要由PABPN 1组成的核内包涵体已被认为是遗传性疾病的病理标志。为了阐明导致疾病的分子事件，分析了重组PABPN 1和具有不同聚-L-丙氨酸延伸的蛋白质的N-末端片段。由于全长蛋白质表现出聚集成无定形沉积物的强烈倾向，因此还研究了可溶性N末端片段。在OPMD患者中观察到的聚-L-丙氨酸序列扩展至最大长度导致α-螺旋结构增加。在长时间孵育后，在显示淀粉样纤维的所有特征的原纤维中发现该蛋白质。接种可以减少纤维形成的滞后期。原纤维的结构分析表明反平行β-折叠。
The nuclear poly(A) binding protein (PABPN1) stimulates poly(A) polymerase and controls the lengths of poly(A) tails during pre-mRNA processing. The wild-type protein possesses 10 consecutive Ala residues immediately after the start methionine. Trinucleotide expansions in the coding sequence result in an extension of the Ala stretch to maximal 17 Ala residues in total. Individuals carrying the trinucleotide expansions suffer from oculopharyngeal muscular dystrophy (OPMD). Intranuclear inclusions consisting predominantly of PABPN1 have been recognized as a pathological hallmark of the genetic disorder. To elucidate the molecular events that lead to disease, recombinant PABPN1, and N-terminal fragments of the protein with varying poly-L-alanine stretches were analyzed. As the full-length protein displayed a strong tendency to aggregate into amorphous deposits, soluble N-terminal fragments were also studied. Expansion of the poly-L-alanine sequence to the maximal length observed in OPMD patients led to an increase of alpha-helical structure. Upon prolonged incubation the protein was found in fibrils that showed all characteristics of amyloid-like fibers. The lag-phase of fibril formation could be reduced by seeding. Structural analysis of the fibrils indicated antiparallel beta-sheets.