The Euplotes La motif protein p43 has properties of a telomerase-specific subunit
The Euplotes La motif protein p43 has properties of a telomerase-specific subunit
复制标题
DOI：
10.1021/bi034121y
复制
发表时间：
2003-05-20
期刊：
影响因子：
2.9
通讯作者：
Cech, TR
中科院分区：
文献类型：
--
作者：
Aigner, S;Postberg, J;Cech, TR
端粒酶是一种合成端粒DNA重复序列的逆转录酶。除了RNA和催化蛋白组分外，来自纤毛类昆虫Euplotes aediculatus的端粒酶还含有亚基p43。这种蛋白质与La自身抗原同源，在RNA聚合酶III转录物的成熟中起作用。在这里，我们提供的证据表明，p43主要与端粒酶核糖核蛋白在体内。重组p43在体外以低纳摩尔亲和力结合端粒酶RNA，识别RNA核心中的茎I和相邻核苷酸或结构。与真正的La蛋白不同，p43不与RNA聚合酶III前体转录物强烈结合，并且不表现出对3 '-末端寡核苷酸残基的明显结合偏好。在分离的大核中，p43主要与端粒酶RNA共定位在离散的病灶中。这些发现表明，p43不是游仆虫La蛋白，而是在端粒酶组装和/或功能中起着专门的作用。因此，p43加入端粒酶逆转录酶和酵母蛋白Est 1 p和Est 3 p作为迄今为止唯一鉴定的端粒酶特异性蛋白。
Telomerase is a specialized reverse transcriptase synthesizing DNA repeats at telomeres. In addition to the RNA and catalytic protein components, telomerase from the ciliate Euplotes aediculatus contains the subunit p43. This protein is homologous to the La autoantigen, functioning in maturation of RNA polymerase III transcripts. Here we provide evidence that p43 is primarily associated with the telomerase ribonucleoprotein in vivo. Recombinant p43 binds telomerase RNA with low-nanomolar affinity in vitro, recognizing stem I and adjacent nucleotides or structures in the core of the RNA. Unlike authentic La proteins, p43 does not bind strongly to RNA polymerase III precursor transcripts and does not exhibit a marked binding preference for 3'-terminal oligouridylate residues. In isolated macronuclei, p43 largely colocalizes with telomerase RNA in discrete foci. These findings suggest that p43 is not the Euplotes La protein but instead plays a dedicated role in telomerase assembly and/or function. Thus, p43 joins the telomerase reverse transcriptase and the yeast proteins Est1p and Est3p as the only telomerase-specific proteins identified so far.