|MadSci Network: Cell Biology|
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. Bye! Mike.
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