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首页> 外文期刊>Molecular and Cellular Biology >Identification and characterization of a putative telomere end-binding protein from Tetrahymena thermophila.
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Identification and characterization of a putative telomere end-binding protein from Tetrahymena thermophila.

机译：鉴定和鉴定嗜热四膜虫的端粒末端结合蛋白。

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Telomeric DNA of Tetrahymena thermophila consists of a long stretch of (TTGGGG)n double-stranded repeats with a single-stranded (TTGGGG)2 3' overhang at the end of the chromosome. We have identified and characterized a protein that specifically binds to a synthetic telomeric substrate consisting of duplex DNA and the 3' telomeric repeat overhang. This protein is called TEP (telomere end-binding protein). A change from G to A in the third position of the TTGGGG overhang repeat converts the substrate to a human telomere analog and reduces the binding affinity approximately threefold. Changing two G's to C's in the TTGGGG repeats totally abolishes binding. However, permutation of the Tetrahymena repeat sequence has only a minor effect on binding. A duplex structure adjacent to the 3' overhang is required for binding, although the duplex need not contain telomeric repeats. TEP does not bind to G-quartet DNA, which is formed by many G-rich sequences. TEP has a greatly reduced affinity for RNA substrates. The copy number of TEP is at least 2 x 10(4) per cell, and it is present under different conditions of cell growth and development, although its level varies. UV cross-linking experiments show that TEP has an apparent molecular mass of approximately 65 kDa. Unlike other telomere end-binding proteins, TEP is sensitive to high salt concentrations.
机译：嗜热四膜菌的端粒DNA由长链（TTGGGG）n双链重复序列组成，在染色体末端带有单链（TTGGGG）2 3'突出端。我们已经鉴定并鉴定了一种蛋白质，该蛋白质与由双链DNA和3'端粒重复突出端组成的合成端粒底物特异性结合。这种蛋白质称为TEP（端粒末端结合蛋白）。 TTGGGG突出端重复序列的第三位置从G变为A会将底物转化为人类端粒类似物，并使结合亲和力降低约三倍。将TTGGGG中的两个G更改为C会完全取消绑定。但是，四膜虫重复序列的排列对结合的影响很小。结合需要一个与3'突出端相邻的双链体结构，尽管该双链体不必包含端粒重复序列。 TEP不结合由许多富含G的序列形成的G四重奏DNA。 TEP对RNA底物的亲和力大大降低。 TEP的拷贝数至少为每个细胞2 x 10（4），尽管其水平有所不同，但它在不同的细胞生长和发育条件下存在。紫外线交联实验表明，TEP的表观分子量约为65 kDa。与其他端粒末端结合蛋白不同，TEP对高盐浓度敏感。

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