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首页> 外文期刊>Molecular and Cellular Biology >Separation of factors required for cleavage and polyadenylation of yeast pre-mRNA.
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Separation of factors required for cleavage and polyadenylation of yeast pre-mRNA.

机译：分离酵母前mRNA的裂解和聚腺苷酸所需的因子。

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Cleavage and polyadenylation of yeast precursor RNA require at least four functionally distinct factors (cleavage factor I [CF I], CF II, polyadenylation factor I [PF I], and poly(A) polymerase [PAP]) obtained from yeast whole cell extract. Cleavage of precursor occurs upon combination of the CF I and CF II fractions. The cleavage reaction proceeds in the absence of PAP or PF I. The cleavage factors exhibit low but detectable activity without exogenous ATP but are stimulated when this cofactor is included in the reaction. Cleavage by CF I and CF II is dependent on the presence of a (UA)6 sequence upstream of the GAL7 poly(A) site. The factors will also efficiently cleave precursor with the CYC1 poly(A) site. This RNA does not contain a UA repeat, and processing at this site is thought to be directed by a UAG...UAUGUA-type motif. Specific polyadenylation of a precleaved GAL7 RNA requires CF I, PF I, and a crude fraction containing PAP activity. The PAP fraction can be replaced by recombinant PAP, indicating that this enzyme is the only factor in this fraction needed for the reconstituted reaction. The poly(A) addition step is also dependent on the UA repeat. Since CF I is the only factor necessary for both cleavage and poly(A) addition, it is likely that this fraction contains a component which recognizes processing signals located upstream of the poly(A) site. The initial separation of processing factors in yeast cells suggests both interesting differences from and similarities to the mammalian system.
机译：酵母前体RNA的裂解和聚腺苷酸化需要至少四个从酵母全细胞提取物中获得的功能上不同的因子（裂解因子I [CF I]，CF II，聚腺苷酸化因子I [PF I]和poly（A）聚合酶[PAP]） 。 CF I和CF II馏分结合后会发生前体裂解。裂解反应在没有PAP或PF I的情况下进行。裂解因子在没有外源ATP的情况下显示出低但可检测的活性，但是当该辅因子包含在反应中时会被激活。 CF I和CF II的切割取决于GAL7 poly（A）位点上游（UA）6序列的存在。这些因素还将有效裂解具有CYC1 poly（A）位点的前体。该RNA不包含UA重复序列，因此该位点的加工被认为是由UAG ... UAUGUA型基序指导的。预切割的GAL7 RNA的特定聚腺苷酸化作用需要CF I，PF I和含有PAP活性的粗馏分。 PAP馏分可以用重组PAP代替，表明该酶是该馏分中重组反应所需的唯一因子。 poly（A）添加步骤还取决于UA重复。由于CF I是裂解和添加poly（A）所需的唯一因素，因此该馏分很可能包含识别位于poly（A）位点上游的处理信号的成分。酵母细胞中加工因子的初步分离表明与哺乳动物系统有趣的区别和相似之处。

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