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In eukaryote cells, RNA polymerase III (also called Pol III) transcribes DNA to synthesize ribosomal 5S rRNA, tRNA and other small RNAs. This enzyme complex has a more limited role than the Pol III in prokaryote cells. The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose expression is required in all cell types and most environmental conditions. Therefore the regulation of Pol III transcription is primarily tied to the regulation of cell growth and the cell cycle, thus requiring fewer regulatory proteins than RNA polymerase II. Under stress conditions however, the protein Maf1 represses Pol III activity. In the process of transcription (by any polymerase) there are three main stages: #Initiation; requiring construction of the RNA polymerase complex on the gene's promoter. #Elongation; the synthesis of the RNA transcript. #Termination; the finishing of RNA transcription and disassembly of the RNA polymerase complex. ==Initiation== Initiation: the construction of the polymerase complex on the promoter. Pol III is unusual (compared to Pol II) requiring no control sequences upstream of the gene, instead normally relying on internal control sequences - sequences within the transcribed section of the gene (although upstream sequences are occasionally seen, e.g. U6 snRNA gene has an upstream TATA box as seen in Pol II Promoters). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「RNA polymerase III」の詳細全文を読む スポンサード リンク
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