MadSci Network: Cell Biology

Re: Without RNA polymerase can transcription still occur?

Date: Thu Mar 16 09:36:35 2000
Posted By: Michel Ouellette, Grad Student in Microbiology/Immunology
Area of science: Cell Biology
ID: 952646906.Cb

Hello to you all,

Thank you for your question, it is my pleasure to answer it.

RNA polymerases are a group of enzyme that can take two ribonucleotides 
(RNA) and polymerize or "connect" them together.  If such an enzyme does 
this with the same strand of RNA a hundred times, you end up with a RNA 
molecule of a hundred bases.

Since any molecule that can do that would de facto be called a RNA 
polymerase, the absence of such an activity in the cell would lead to the 
arrest of the RNA transcription.

Because this activity is so important for the cell, however, it is always 
present.  Some viruses are able to subvert the transcription system of the 
cells they infect and direct the cellular RNA polymerase to transcribe only 
viral DNA.  Another strategy used by some viruses is to produce their own 
RNA polymerase and destroy the RNA polymerase of the cell.  This is very 
damaging to the cell and all of these kind of viruses end up killing their 
host cell.

In mammals, there is three types of RNA polymerases( I, II and III).  Each 
of these types transcribe RNAs for different uses.  The RNA polymerase I is 
responsible for the transcription of ribosomal RNA (rRNA; important for 
RNA translation), the RNA polymerase III is responsible for the 
transcription of transfert RNA (tRNA; important for RNA translation) and 
the RNA polymerase II is responsible for the transcription of messenger RNA 
(mRNA) which are those that are translated in proteins by ribosomes.

Each of the polymerase have different ways to initiate RNA transcription 
and they cannot take each other places.  The absence of any of these RNA 
polymerases would lead to cell death very rapidly.

I hope this answered your question and helped you a little,

If you want more details, don't hesitate to ask.



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