RNA Polymerase: Function, Types, and Definition

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What is RNA Polymerase?

RNA polymerase plays an important role in carrying out the process of transcription. Transcription is a process where the genes of a DNA sequence is transcribed to make a molecule of RNA, where RNA polymerase plays an important role in this process.

Transcription begins when the enzyme RNA polymerase binds to the sequence of promoter beside the beginning of a gene sequencing either directly or through the helper proteins.

RNA polymerase uses one of the strands of the DNA, as a template; so, the strand of DNA is mentioned as template strand which makes a new molecule of complementary RNA and transcription ends in a process called termination.

Where termination depends on the sequence of the RNA, where the signal arises when the transcription is complete.

RNA polymerase is considered as one of the crucial enzymes as it carries out the process of transcription, where the process of copying the genetic material Deoxyribose ribonucleic acid into the Ribonucleic acid (RNA).

Because transcription is one of the most vital steps involved in using the information from genes in our DNA to make the essential proteins, Proteins act as key molecule which gives a cell structure and helps in running them continuously.

Generally, mushrooms have their lethal effect in producing the specific toxin, that attaches it to the crucial enzyme in our body, which is RNA polymerase.

Blocking the transcription process with the mushroom toxin causes many defects like liver failure and even death, because there will no RNA so no proteins will be produced. So, transcription is very much important in caring out a life process.

Role of RNA Polymerase in Transcription

RNA polymerases are the enzymes which transcribe the DNA into the RNA. Using the DNA template, this enzyme RNA polymerases builds a new molecule of RNA through base pairing.

For example, if there is any G i.e., Guanine in the DNA template, RNA polymerases act a C (cytosine) to the new developing strand of RNA.

RNA polymerases always build a new RNA strand in the direction of 5’ to 3’ end which helps in adding the nucleotides to the 3’ end of the strand.

RNA polymerases are usually the large enzymes which has multiple sub units even in the lower organisms like bacteria.

Where as the eukaryotes and humans have three variety of RNA polymerases, named as RNA Polymerase – I, II and III.

Each of this type has specialising transcribing factors in certain classes of genes.

Plants have additional polymerases apart from this as IV and V, which plays an important role in producing certain small RNAs.

RNA Polymerase in Initiating Transcription

To initiate the process of transcription by transcribing a gene, RNA polymerases act as a binding agent by binding to the DNA of the gene at the regions known as promoter.

Generally, this promoter conveys a message to the polymerase that where it has to be positioned on the DNA and where it has to start transcribing.

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Each gene contains its own promoter, where the promoter contains the sequence of DNA which lets either the enzyme RNA Polymerase or its helper proteins to attach to the DNA. When the transcription bubble is formed, polymerase starts transcribing.

RNA Polymerase, Promoters, and Bacteria

Promoter in bacteria stands as a best example of how a polymerase works, Bacteria contains two types of important sequences of DNA, -10 and -35 elements.

RNA polymerases recognise and binds straitly to these sequences, where these sequences position the polymerase enzymes in the appropriate spot and initiates the transcribing in the target gene, and it also ensures the pointing that it acts in a right direction.

Once the enzyme RNA polymerase bounds up it opens the DNA and starts to function. Opening of DNA occurs at the -10 element, Here the strands can be separated easily because of the factors such as As and Ts, which helps in binding to each other with the hydrogen bonds.

The elements -10 and -35 derives its name from the nucleotides 35 and 10. The minus sign is denoted just to show that they are before the site of initiation.

RNA Polymerase, Promoters, and Humans

In eukaryotes like mammals and humans, the RNA polymerase in the cells does not directly attaches to promoters like that of the polymerases in the bacteria.

Instead of this helper proteins which are called as basal transcription factors which first binds to the promoters, and helps the RNA polymerases in the cells to get hold on to the DNA.

Several eukaryotic promoters consist of a sequence known as TATA box, which plays an important role similar to that of the -10 element.

It is actually recognised by the general transcription factors, which allows the other transcription factors and also the RNA polymerases to bind eventually.

It also contains a lot of As and Ts, which also makes it very easy to pull the strands of the part of DNA.

RNA Polymerase and Elongation

When the enzyme, RNA polymerase is positioned at the site of promoter, the next step of transcription begins, which is known as elongation.

Elongation is the stage where the strands of RNA get longer. During elongation these RNA polymerases moves along the single strand of DNA, which is commonly called as template strand in the direction of 3’ to 5’.

Each nucleotide in a template needs RNA polymerases to match it with a nucleotide of an RNA at a 3’ end in the RNA strand.

RNA Polymerase and Termination

RNA polymerases transcribe until the signals gets stopped. Ending the process of transcription is generally known as termination and it happens only when the polymerase transcribes one of sequence of DNA which is known as terminator.

RNA Polymerase Citations


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