Molecular biology

RNA polymerase Definition, Types, and Functions

Ribonucleic acid (RNA) Polymerase (RNAP) enzyme is a multi-subunit enzyme which uses its function to catalyze the transcription process RNA produced from...

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This article writter by MN Editors on December 28, 2021

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RNA polymerase Definition, Types, and Functions
RNA polymerase Definition, Types, and Functions

Definition of RNA polymerase 

  • Ribonucleic acid (RNA) Polymerase (RNAP) enzyme is a multi-subunit enzyme which uses its function to catalyze the transcription process RNA produced from DNA template.
  • The this enzyme plays a role in transcription of DNA sequences to the RNA sequences that are used during transcription.
  • The purpose of RNA Polymerase is to regulate the transcription process by which DNA information into an entirely new messenger RNA (mRNA.)
  • In the process of transcription the RNA polymer becomes in sync with the template DNA which is synthesized from 5′-3′.
  • The enzyme RNA polymerase works with proteins in order to perform its function by catalyzing the synthesis of RNA.
  • The protein collaborators aid in facilitating the specific interaction of the RNA polymerase. aid in unravelling the double DNA chemical structure as well as regulating the enzymatic functions of RNA polymerase as well as to manage the speed of transcription.
  • The enzyme RNA polymerase has an unreliable mechanism that constantly synthesizes RNA polymers at more than 4000 bases per minute, but they stop or pause periodically to maintain the fidelity.
  • The RNA polymerase enzyme responsible for converting DNA sequences into RNA sequence, in transcription. Since it is a complex molecule made up from protein components, RNA Polymerase regulates the transcription process in which the information stored within DNA molecules is converted into a brand new messenger RNA molecule.
  • RNA polymerases have been identified across all species, however the quantity and nature of these proteins differ across taxa.
  • As an example, bacteria have one type of RNA polymerase. the eukaryotes (multicellular yeasts and other organisms) have three distinct kinds.
  • Despite these differences there are striking similarities in transcriptional mechanisms.
  • For instance each species needs an mechanism through which transcription can be controlled in order to produce time and space-based modifications in gene expression.
RNA polymerase
RNA polymerase

Types of RNA polymerase

Prokaryotic (Bacteria, archaea, viruses) organisms possess one kind of RNA polymerase which synthesizes all subtypes the RNA. Eukaryotes (multicellular organisms) contain five different kinds of RNA polymerases that perform different roles in the synthesis of various RNA molecules.

Prokaryotic RNA polymerase

Prokaryotes are the only type of RNA Polymerase (RNAP) which is responsible for the production of all classes of RNA i.e the mRNA, tRNA the rRNA and SRNA. This RNA Polymerase molecule is made consisting of 2 domains as well as 5 subunits

  • Core and holoenzyme
  • Subunits (β, β’, α (αI and αII), ω,)

Promors are the DNA sequence that is necessary for precise and precise initiation of transcription. Additionally it is the sequence of DNA that RNA polymerase is able to bind precisely to start transcription. The “a” subunit is comprised from two domains. the N-terminal (a-NTD) along with the C-terminal. The N-terminal plays a role in dimerization, forming a2 and an additional assembly process of the RNA polymerase. The C-terminal function is as in binding to the upstream promoter (UP) DNA sequence in promoters of rRNA and tRNA genes, as well as communicating with a variety of transcriptional activators. The structure of each subunit is according to:

Prokaryotic RNA Polymerase Subunits

SubunitSizeFunction
β150.4 kDaThe β’ + β form the catalytic center, responsible for RNA synthesis.
β’155.0 kDaThe β’ + β form the catalytic center, responsible for RNA synthesis.
α (αI and αII)36.5 kDaIt is made up of the enzyme assembly, and it also binds the UP sequence in the promoter.
ω155.0 kDaIt confers specificity for promoter; and binds to -10 and -35 sites in the promoter.

Eukaryotic RNA polymerase

There are five known kinds of RNA polymerases that are each involved in the synthesis of subtypes of RNA. They include:

  • RNA polymerase I, which synthesizes a pre-rRNA45S (35S within yeast) that matures and creates the main sections of RNA in the ribosome.
  • RNA polymerase II synthesizes precursors of mRNAs as well as most microRNAs and snRNAs.
  • RNA polymerase III synthesizes tRNAs as well as rRNA 5S and other small RNAs that are found in the cytosol and nucleus.
  • The RNA polymerase IV and V discovered in plants aren’t fully understood, but they create siRNA. The chloroplast in plants encodes ssRNAPs , which is a bacteria-like RNA Polymerase.

Every one of these nuclear polymerases are an enormous protein molecule that has approximately 8-14 subunits. Their molecular weight is around 500 million for each. The most common subunits are including a, b and B’. The most important subunits are the b and the b’. These subunits serve as catalytic promoters , and also for the assembly of proteins. Each of the polymerases performs specific functions:

RNA polymerase I

The enzyme is found in the nucleolus inside the cell. It is a specific nuclear substructure that houses the Ribosomal RNA (rRNA) is synthesized through transcription and assembles into Ribosomes. The rRNA is one of the components of ribosomes and play an crucial in the process of translation. So, RNA polymerase II produces almost all rRNAs, with the exception of 5S rRNA. In yeast the enzyme is found to have an approximate mass of 600kDa as well as 13 subunits.

RNA polymerase II

The enzyme is located inside the nucleus. Most organisms that have the RNA polymerase II enzyme contain 12-subunit RNAP II (with a mass of 525 km2). It is composed of mediators and holoenzyme, along with general Transcriptional Factors (GTFs). They are composed of transcription factors and transcriptional regulators. It works by synthesizing all proteins responsible for the nuclear pre-mRNAs that are found in the eukaryotic cells (mRNAs found in prokaryotic cells). The enzyme is accountable for the transcription of most of the eukaryotic genes , and particularly in human genes.

RNA polymerase III

It is located inside the nucleus. It is located in the nucleus. RNA polymerase III has 14 or more distinct subunits that have a the mass of around 700 kDa. Its primary function is to transscribe transfers RNA (tRNA) and ribosomal (rRNA) as well as others small RNAs. A few of its target areas are crucial in the normal functioning of the cell.

RNA polymerases IV and V

They are found only in plants and play a role in the creation of small interfering RNA as well as heterochromatin inside the nucleus of the cell. In Plants the RNA polymerase is located within the chloroplast (plastids) and mitochondria, encoded by mitochondrial DNA. These enzymes are far more closely related to the bacterial RNA polymerase, than nucleotide RNA polymerase. Their purpose is to catalyze particular transcriptional activity of organelle gene expression.

Functions of RNA Polymerase

  • In general, the molecules of RNA are an RNA messenger molecule utilized to transfer information encoded in DNA that is released from the nucleus of the cell, to produce proteins within the cell’s the cytoplasm.
  • The RNA polymerase is utilized to create molecules that perform a broad variety of functions, of which one is to control the quantity and types of RNA transcripts produced in response to the needs of cells.
  • The enzyme RNA Polymerase is in contact with a variety of molecular proteins, transcription factors and signaling molecules located on the carboxyl-terminal. This regulates its actions, which are crucial to the expression of genes and the specialization of genes within multicellular (eukaryotic) organisms.
  • The RNA enzyme is also responsible for inconsistencies and errors when converting DNA into the form of RNA (transcription). For instance, making sure the correct nucleotide is placed in an RNA strand that has been synthesized strand by inserting the appropriate amino acid base that is compatible with the DNA template strand.
  • Once the correct nucleotides are inserted and the RNA polymerase has been activated, it will be catalyzed and then elongate the RNA strand. At simultaneously, it will proofread the new strand, and eliminate indecent bases.
  • The RNA polymerase also participates in the post-transcriptional modification of RNAs. It converts these into useful molecules which assist the transport of these molecules out from their nuclei and to their place of action.
  • Apart from its function in the production of proteins, RNA also serves other purposes like
    • Protein coding
    • Control of expression genes
    • Act as enzymes
    • Gametes are formed by non-coding gametes is facilitated by the non-coding (ncRNA)
    • The production of molecules that regulate.

RNA polymerase vs DNA polymerase

DNA polymerase creates double-stranded molecules by separating DNA strands from their unwound form when it is replicating. Although the final products of transcription and replication are distinct, they each work on DNA by introducing nucleotides in the same 5′-3 direction. Contrary to RNA polymerase, DNA Polymerase is semi-conserved process that makes use of both strands of the double-stranded DNA molecule to serve as the template to replicate.

ComparisonRNA PolymeraseDNA Polymerase
FunctionTranscription of DNADNA replication
ScopeTo create DNA copies of genesTo duplicate the whole genome
The time of the eventIt is used in transcription in transcription G phase(s)In replication, it is utilized during S phase
PrimerNot necessary to be transcribedRequired to initiate replication
Base pairs are the components used to synthesize productsAdenine, Guanine, Cytosine and UracilAdenine, Guanine, Cytosine and Thymine
The product that resultsSingle-strandedRNAs (e.g. mRNA)Double-stranded DNA

RNA polymerase and drugs

The RNA polymerase is a popular drug target because of its widespread existence and its function throughout the entire life. The biochemical variations in RNA polymerase among prokaryotes and eukaryotes enable the use of specific drugs to target microbiological RNA polymerases, without connection to our own.

Many antimicrobial medications serve as inhibitors of RNA polymerase by blocking viral or bacterial enzyme activity in one phase of transcription. For instance the rifamycins5 belong to an antibiotic group from bacteria which inhibit elongation through inhibiting the exit channels of the RNA polymerase. They are frequently employed to treat serious illnesses caused by leprosy or tuberculosis.

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Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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