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Abstract:
Whereas mechanisms underlying the fidelity of DNA
polymerases (DNAPs) have been investigated in detail, RNA
polymerase (RNAP) fidelity mechanisms remained poorly
understood. New functional and structural studies now suggest
how RNAPs select the correct nucleoside triphosphate (NTP)
substrate to prevent transcription errors, and how the enzymes
detect and remove a misincorporated nucleotide during
proofreading. Proofreading begins with fraying of the
misincorporated nucleotide away from the DNA template,
which pauses transcription. Subsequent backtracking of RNAP
by one position enables nucleolytic cleavage of an RNA
dinucleotide that contains the misincorporated nucleotide.
Since cleavage occurs at the same active site that is used for
polymerization, the RNAP proofreading mechanism differs
from that used by DNAPs, which contain a distinct nuclease
specific active site.
