Initiation and regulation mechanisms of ribosomal RNA transcription in the eukaryote Acanthamoeba castellanii.
Initiation and regulation mechanisms of ribosomal RNA transcription in the eukaryote Acanthamoeba castellanii.
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真核生物卡氏棘阿米巴核糖体 RNA 转录的启动和调节机制。
DOI：
10.1007/bf00229811
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发表时间：
1991
影响因子：
4.3
通讯作者：
Risi,P
中科院分区：
文献类型：
--
作者：
Paule,MR;Bateman,E;Hoffman,L;Iida,C;Imboden,M;Kubaska,W;Kownin,P;Li,H;Lofquist,A;Risi,P
阿米巴RNA转录涉及转录起始因子（TIF）与rDNA核心启动子结合形成前起始复合物。该复合物在RNA聚合酶I不存在的情况下形成，并持续多轮起始。聚合酶I接着结合形成起始复合物。这种结合不依赖于DNA序列，并且通过与TIF的蛋白质-蛋白质接触来指导。DNA解链发生在单独的步骤中。与大多数原核转录相反，解链仅在添加核苷酸后发生，并且不需要像聚合酶II那样进行ATP的β-γ水解。rRNA转录的生长依赖性调节是通过RNA聚合酶I的修饰完成的。聚合酶（PolE）的非活性形式不能与启动子结合，并且具有改变的热稳定性。PolE在延伸中仍有活性;因此，修饰影响了与TIF接触有关的聚合酶位点。已检测到聚合酶I和III共同亚基的修饰，从而表明核糖体的稳定RNA的转录可能受此机制的共同调节。
AcanthamoebarRNA transcription involves the binding of a transcription initiation factor (TIF) to the core promoter of rDNA to form the preinitiation complex. This complex is formed in the absence of RNA polymerase I, and persists for multiple rounds of initiation. Polymerase I next binds to form the initiation complex. This binding is DNA sequence-independent, and is directed by protein-protein contacts with TIF. DNA melting occurs in a separate step. In contrast to most prokaryotic transcription, melting occurs only following nucleotide addition and β-γ hydrolysis of ATP is not required as for polymerase II. Growth-dependent regulation of rRNA transcription is accomplished by modification of RNA polymerase I. The inactive form of polymerase (PolE) is unable to bind to the promoter and has altered heat stability. PolEis still active in elongation; thus, the modification affects the polymerase site involved in TIF contact. Modification of a polymerases I and III common subunit has been detected leading to the suggestion that transcription of stable RNAs of the ribosome might be co-regulated by this mechanism.