Group II intron splicing factors derived by diversification of an ancient RNA-binding domain
Group II intron splicing factors derived by diversification of an ancient RNA-binding domain
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DOI：
10.1093/emboj/cdg372
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发表时间：
2003-08-01
期刊：
影响因子：
11.4
通讯作者：
Barkan, A
中科院分区：
文献类型：
--
作者：
Ostheimer, GJ;Williams-Carrier, R;Barkan, A
II组内含子是核酶，其催化机制与剪接体的催化机制非常相似。许多第二组内含子已经失去了自主剪接的能力，作为一个进化过程的结果，在该过程中，自我剪接活性的损失被补偿的招聘主机编码的蛋白质辅因子。先前的遗传筛选确定了CRS 1和CRS 2作为玉米叶绿体中II组内含子剪接所需的宿主编码蛋白。在这里，我们描述了两个额外的主机编码的第二组内含子剪接因子，CRS 2相关因子1和2（CAF 1和CAF 2）。我们表明，CRS 2功能的背景下，内含子核糖核蛋白颗粒，包括CAF 1或CAF 2，CRS 2-CAF 1和CRS 2-CAF 2复合物具有不同的内含子特异性。CAF 1、CAF 2和先前描述的II组内含子剪接因子CRS 1的特征在于相似的重复结构域，我们在此将其命名为CRM（叶绿体RNA剪接和核糖体成熟）结构域。我们认为CRM结构域是一个古老的RNA结合模块，它已经多样化以介导与各种高度结构化的RNA的特异性相互作用。
Group II introns are ribozymes whose catalytic mechanism closely resembles that of the spliceosome. Many group II introns have lost the ability to splice autonomously as the result of an evolutionary process in which the loss of self-splicing activity was compensated by the recruitment of host-encoded protein cofactors. Genetic screens previously identified CRS1 and CRS2 as host-encoded proteins required for the splicing of group II introns in maize chloroplasts. Here, we describe two additional host-encoded group II intron splicing factors, CRS2-associated factors 1 and 2 (CAF1 and CAF2). We show that CRS2 functions in the context of intron ribonucleoprotein particles that include either CAF1 or CAF2, and that CRS2-CAF1 and CRS2-CAF2 complexes have distinct intron specificities. CAF1, CAF2 and the previously described group II intron splicing factor CRS1 are characterized by similar repeated domains, which we name here the CRM (chloroplast RNA splicing and ribosome maturation) domains. We propose that the CRM domain is an ancient RNA-binding module that has diversified to mediate specific interactions with various highly structured RNAs.