RNA polymerase

(noun)

a DNA-dependent RNA polymerase, an enzyme, that produces RNA

Related Terms

Examples of RNA polymerase in the following topics:

  • Elongation and Termination in Eukaryotes

    • RNA Polymerase II will continue to elongate the newly-synthesized RNA until transcription terminates.
    • RNA Polymerase II is a complex of 12 protein subunits.
    • The tRNA, 5S rRNA, and structural RNAs genes transcribed by RNA Polymerase III have a not-entirely-understood termination signal.
    • The RNAs transcribed by RNA Polymerase III have a short stretch of four to seven U's at their 3' end.
    • Xrn2 will start digesting the non-released portion of the newly synthesized RNA until Xrn2 reaches the RNA Polymerase, where it aids in displacing the RNA Polymerase from the template DNA strand.

  • Initiation of Transcription in Eukaryotes

    • RNA polymerase I synthesizes all of the rRNAs except for the 5S rRNA molecule.
    • RNA polymerase II is located in the nucleus and synthesizes all protein-coding nuclear pre-mRNAs.
    • RNA polymerase III is also located in the nucleus.
    • This polymerase transcribes a variety of structural RNAs that includes the 5S pre-rRNA, transfer pre-RNAs (pre-tRNAs), and small nuclear pre-RNAs.
    • Not all miRNAs are transcribed by RNA Polymerase II, RNA Polymerase III transcribes some of them.

  • The Promoter and the Transcription Machinery

    • RNA polymerase binds to the transcription initiation complex, allowing transcription to occur.
    • Once this transcription initiation complex is assembled, RNA polymerase can bind to its upstream sequence.
    • When bound along with the transcription factors, RNA polymerase is phosphorylated.
    • A generalized promoter of a gene transcribed by RNA polymerase II is shown.
    • RNA polymerase II then binds and forms the transcription initiation complex.

  • Initiation of Transcription in Prokaryotes

    • Prokaryotes use the same RNA polymerase to transcribe all of their genes.
    • Each subunit has a unique role: the two α-subunits are necessary to assemble the polymerase on the DNA; the β-subunit binds to the ribonucleoside triphosphate that will become part of the nascent "recently-born" mRNA molecule; and the β' binds the DNA template strand.
    • It confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site.
    • The polymerase comprised of all five subunits is called the holoenzyme.
    • The σ subunit of prokaryotic RNA polymerase recognizes consensus sequences found in the promoter region upstream of the transcription start sight.

  • Elongation and Termination in Prokaryotes

    • The dissociation of σ allows the core RNA polymerase enzyme to proceed along the DNA template, synthesizing mRNA in the 5' to 3' direction at a rate of approximately 40 nucleotides per second.
    • Since the base pairing between DNA and RNA is not stable enough to maintain the stability of the mRNA synthesis components, RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely.
    • Rho-dependent termination is controlled by the rho protein, which tracks along behind the polymerase on the growing mRNA chain.
    • This, coupled with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript.
    • During elongation, the prokaryotic RNA polymerase tracks along the DNA template, synthesizes mRNA in the 5' to 3' direction, and unwinds and rewinds the DNA as it is read.

  • mRNA Processing

    • While RNA Polymerase II is still transcribing downstream of the proper end of a gene, the pre-mRNA is cleaved by an endonuclease-containing protein complex between an AAUAAA consensus sequence and a GU-rich sequence.
    • This releases the functional pre-mRNA from the rest of the transcript, which is still attached to the RNA Polymerase.
    • An enzyme called poly (A) polymerase (PAP) is part of the same protein complex that cleaves the pre-mRNA and it immediately adds a string of approximately 200 A nucleotides, called the poly (A) tail, to the 3' end of the just-cleaved pre-mRNA.
    • Poly (A) Polymerase adds a 3' poly (A) tail to the pre-mRNA.
    • The pre-mRNA is cleaved off the rest of the growing transcript before RNA Polymerase II has stopped transcribing.

  • The Protein Synthesis Machinery

    • Protein synthesis, or translation of mRNA into protein, occurs with the help of ribosomes, tRNAs, and aminoacyl tRNA synthetases.
    • The tRNA molecules are transcribed by RNA polymerase III.
    • The transfer RNAs (tRNAs) are structural RNA molecules.
    • In eukaryotes, tRNA mole are transcribed from tRNA genes by RNA polymerase III.
    • The process of pre-tRNA synthesis by RNA polymerase III only creates the RNA portion of the adaptor molecule.

  • DNA Replication in Eukaryotes

    • All newly synthesized polynucleotide strands must be initiated by a specialized RNA polymerase called primase.
    • This short stretch of RNA nucleotides is called the primer.
    • Once RNA primer has been synthesized at the template DNA, primase exits, and DNA polymerase extends the new strand with nucleotides complementary to the template DNA.
    • DNA polymerase can only synthesize new strands in the 5' to 3' direction.
    • An RNA primer is synthesized by primase and is elongated by the DNA polymerase.

  • The Central Dogma: DNA Encodes RNA and RNA Encodes Protein

    • The central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein.
    • During transcription, a DNA sequence is read by RNA polymerase, which produces a complementary, antiparallel RNA strand.
    • This method of synthesizing proteins is directed by the mRNA and accomplished with the help of a ribosome, a large complex of ribosomal RNAs (rRNAs) and proteins.
    • Transfer RNA, or tRNA, translates the sequence of codons on the mRNA strand.
    • Instructions on DNA are transcribed onto messenger RNA.

  • DNA Replication in Prokaryotes

    • Another enzyme, RNA primase, synthesizes an RNA primer that is about five to ten nucleotides long and complementary to the DNA, priming DNA synthesis.
    • DNA polymerase then extends this RNA primer, adding nucleotides one by one that are complementary to the template strand.
    • As synthesis proceeds, the RNA primers are replaced by DNA.
    • Primase synthesizes an RNA primer.
    • DNA polymerase I replaces the RNA primer with DNA.