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RNA polymerase III (Pol III) transcribes small non-coding RNAs, including tRNAs, 5S rRNA, U6 snRNA, SRP RNA, and other stable short RNAs such as ribonuclease P RNA. [7] Structure of eukaryotic RNA polymerase II (light blue) in complex with α-amanitin (red), a strong poison found in death cap mushrooms that targets this vital enzyme
In archaea and eukaryotes, RNA polymerase contains subunits homologous to each of the five RNA polymerase subunits in bacteria and also contains additional subunits. In archaea and eukaryotes, the functions of the bacterial general transcription factor sigma are performed by multiple general transcription factors that work together. [ 6 ]
The 2006 Nobel Prize in Chemistry was awarded to Roger D. Kornberg for creating detailed molecular images of RNA polymerase during various stages of the transcription process. [3] [4] In most prokaryotes, a single RNA polymerase species transcribes all types of RNA.
In eukaryote cells, RNA polymerase III (also called Pol III) is a protein that transcribes DNA to synthesize 5S ribosomal RNA, tRNA, and other small RNAs. 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.
Many viruses replicate this way. The enzymes that copy RNA to new RNA, called RNA-dependent RNA polymerases, are also found in many eukaryotes where they are involved in RNA silencing. [11] RNA editing, in which an RNA sequence is altered by a complex of proteins and a "guide RNA", could also be seen as an RNA-to-RNA transfer.
Transcription preinitiation complex, represented by the central cluster of proteins, causes RNA polymerase to bind to target DNA site. The PIC is able to bind both the promoter sequence near the gene to be transcribed and an enhancer sequence in a different part of the genome, allowing enhancer sequences to regulate a gene distant from it.
In eukaryotes, three kinds of RNA—rRNA, tRNA, and mRNA—are produced based on the activity of three distinct RNA polymerases, whereas, in prokaryotes, only one RNA polymerase exists to create all kinds of RNA molecules. [3] RNA polymerase II of eukaryotes transcribes the primary transcript, a transcript destined to be processed into mRNA ...
Gene structure is the organisation of specialised sequence elements within a gene.Genes contain most of the information necessary for living cells to survive and reproduce. [1] [2] In most organisms, genes are made of DNA, where the particular DNA sequence determines the function of the gene.