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'''RNA polymerases''', often abbreviated to '''RNAP''', are the enzymes in a cell responsible for [[transcription|synthesizing]] strands of [[RNA]].  Because this function is essential to life, all organisms (and quite a few viruses) contain at least one type of RNA polymerase.  Depending on the RNA polymerase, transcription requires either a [[DNA]] or an RNA template; although in most contexts, "RNA polymerase" refers to the DNA-dependant RNA polymerases, which use a DNA template to [[transcribe|transcription]] genes into [[mRNA]] ("messenger" RNA).  [[reverse transcriptase|Reverse transcriptases]] are enzymes (usually associated with [[retrovirus|retroviruses]]) that perform the opposite function, using an RNA template to synthesize a [[DNA]] product.

'''RNA polymerases''', often abbreviated to '''RNAP''', are the enzymes in a cell responsible for [[transcription|synthesizing]] strands of [[RNA]].  Because this function is essential to life, all organisms (and quite a few viruses) contain at least one type of RNA polymerase.  Depending on the RNA polymerase, transcription requires either a [[DNA]] or an RNA template; although in most contexts, "RNA polymerase" refers to the DNA-dependant RNA polymerases, which use a DNA template to [[transcription|transcribe]] genes into [[mRNA]] ("messenger" RNA).  [[reverse transcriptase|Reverse transcriptases]] are enzymes (usually associated with [[retrovirus|retroviruses]]) that perform the opposite function, using an RNA template to synthesize a [[DNA]] product.

==Types==

==Types==

RNA polymerase II (abbreviated RNAP II or RNA Pol II), is the enzyme responsible for transcribing the vast majority of protein-coding genes in eukaryotes.  It is also responsible for transcribing the majority of genes encoding [[snRNA|short nuclear RNAs]] (snRNAs) and [[miRNA|micro RNAs]] (miRNAs).  As such, RNAP II is the most well-studied and well understood of the eukaryotic RNAPs.  Genes transcribed by RNAP II are referred to as "type II genes" and comprise the vast majority of genes present in eukaryotic genomes.

RNA polymerase II (abbreviated RNAP II or RNA Pol II), is the enzyme responsible for transcribing the vast majority of protein-coding genes in eukaryotes.  It is also responsible for transcribing the majority of genes encoding [[snRNA|short nuclear RNAs]] (snRNAs) and [[miRNA|micro RNAs]] (miRNAs).  As such, RNAP II is the most well-studied and well understood of the eukaryotic RNAPs.  Genes transcribed by RNAP II are referred to as "type II genes" and comprise the vast majority of genes present in eukaryotic genomes.

RNA polymerase I (RNAP I or RNA Pol I) transcribes most of the [[rRNA|ribosomal RNAs]] in a eukaryotic cell. RNA polymerase III (RNAP III or RNA pol III) transcribes the [[transfer RNA|tRNA]] precursors, as well as the 5S rRNA, the U6 snRNA (involved in [[RNA processing|RNA splicing]])and various other small functional RNA products.

RNA polymerase I (RNAP I or RNA Pol I) transcribes most of the [[rRNA|ribosomal RNAs]] in a eukaryotic cell (most of which are derived from a single transcript called the "large rRNA precursor").

 

RNA polymerase III (RNAP III or RNA pol III) transcribes the [[transfer RNA|tRNA]] precursors, as well as the 5S rRNA, the U6 snRNA (involved in [[RNA processing|RNA splicing]])and various other small functional RNA products.

 

 

 

 

1. Alberts et al. (2008). ''Molecular biology of the cell''.