Four factors are required for 3'-end cleavage of pre-mRNAs.
Four factors are required for 3'-end cleavage of pre-mRNAs.
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DOI：
10.1101/gad.3.11.1711
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发表时间：
1989-11
影响因子：
10.5
通讯作者：
Y. Takagaki;L. Ryner;J. Manley
中科院分区：
文献类型：
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作者：
Y. Takagaki;L. Ryner;J. Manley
我们以前报道过，真实的多聚腺苷酸化的前体mRNA在体外需要至少两个因素：一个切割/特异性因子（CSF）和一个馏分含有非特异性聚（A）聚合酶活性。为了研究前体mRNA的3'切割的分子机制，我们进一步分离CSF，并显示其由四个可分离的亚基组成。其中之一，称为特异性因子（SF; Mr，约290，000），是特异性切割和特异性聚腺苷酸化所必需的，因此似乎负责反应的特异性。虽然SF还没有被纯化到同质，几条证据表明，它可能不包含一个基本的RNA成分。另外两种因子，命名为裂解因子I（CFI; Mr，约130，000）和II（CFII; Mr，约110，000），当与SF混合时，足以重建准确的裂解。第四种因子，称为裂解刺激因子（CstF; Mr，约200，000），当加入到其他三种因子的混合物中时，显著增强裂解效率。CFI、CFII和CstF不含RNA组分，在不存在切割的情况下也不影响特异性聚腺苷酸化。虽然这四个因子是必要的，足以重建一个前RNA的有效切割测试，聚（A）聚合酶也需要切割其他几个。一个模型表明这些因素如何相互作用的前mRNA和彼此进行了讨论。
We reported previously that authentic polyadenylation of pre-mRNAs in vitro requires at least two factors: a cleavage/specificity factor (CSF) and a fraction containing nonspecific poly(A) polymerase activity. To study the molecular mechanisms underlying 3' cleavage of pre-mRNAs, we fractionated CSF further and show that it consists of four separable subunits. One of these, called specificity factor (SF; Mr, approximately 290,000), is required for both specific cleavage and for specific polyadenylation and thus appears responsible for the specificity of the reaction. Although SF has not been purified to homogeneity, several lines of evidence suggest that it may not contain an essential RNA component. Two other factors, designated cleavage factors I (CFI; Mr, approximately 130,000) and II (CFII; Mr, approximately 110,000), are sufficient to reconstitute accurate cleavage when mixed with SF. A fourth factor, termed cleavage stimulation factor (CstF; Mr, approximately 200,000), enhances cleavage efficiency significantly when added to a mixture of the three other factors. CFI, CFII, and CstF do not contain RNA components, nor do they affect specific polyadenylation in the absence of cleavage. Although these four factors are necessary and sufficient to reconstitute efficient cleavage of one pre-RNA tested, poly(A) polymerase is also required to cleave several others. A model suggesting how these factors interact with the pre-mRNA and with each other is discussed.