polymerase stuttering
Polymerase stuttering is the process by which a polymerase transcribes a nucleotide several times without progressing further on the mRNA chain. It is often used in addition of poly A tails or capping mRNA chains by less complex organisms such as viruses.
Process
A polymerase may undergo stuttering as a probability controlled event, hence it is not explicitly controlled by any mechanisms in the translation process. Generally, it is a result of many short repeated frameshifts on a slippery sequence of nucleotides on the mRNA strand.{{cite journal | last1 = Anderson | first1 = EC | last2 = Hunt | first2 = SL | last3 = Jackson | first3 = RJ | date = Nov 2007 | title = Internal initiation of translation from the human rhinovirus-2 internal ribosome entry site requires the binding of Unr to two distinct sites on the 5' untranslated region | journal = J Gen Virol | volume = 88 | issue = 11| pages = 3043–52 | doi=10.1099/vir.0.82463-0| doi-access = free | pmid = 17947529 }} However, the frameshift is restricted to one (in some cases two{{cite book | last1 = Mauro | first1 = VP | last2 = Chappell | first2 = SA | last3 = Dresios | first3 = J | chapter = Analysis of Ribosomal Shunting During Translation Initiation in Eukaryotic mRNAs | year = 2007 | title = Translation Initiation: Extract Systems and Molecular Genetics | series = Methods Enzymol | volume = 429 | pages = 323–54 | doi=10.1016/s0076-6879(07)29015-9| pmid = 17913630 | isbn = 978-0-12-374191-2 }}) nucleotides with a pseudoknot or choke points on both sides of the sequence.
Examples
A polymerase that exhibits this behavior is RNA-dependent RNA polymerase, present in many RNA viruses. Reverse transcriptase has also been observed to undergo this polymerase stuttering.{{cite journal | last1 = Kurzynska-Kokorniak | first1 = A | last2 = Jamburuthugoda | first2 = VK | last3 = Bibillo | first3 = A | last4 = Eickbush | first4 = TH | date = Nov 2007 | title = DNA-directed DNA polymerase and strand displacement activity of the reverse transcriptase encoded by the R2 retrotransposon | journal = J Mol Biol | volume = 374 | issue = 2| pages = 322–33 | doi=10.1016/j.jmb.2007.09.047| pmc = 2121658 | pmid=17936300}}
Literature
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