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Action of α-Amanitin during Pyrophosphorolysis and Elongation by RNA Polymerase II
Journal article   Open access   Peer reviewed

Action of α-Amanitin during Pyrophosphorolysis and Elongation by RNA Polymerase II

David R Chafin, Hongliang Guo and David H Price
The Journal of biological chemistry, Vol.270(32), pp.19114-19119
08/11/1995
DOI: 10.1074/jbc.270.32.19114
PMID: 7642577
url
https://doi.org/10.1074/jbc.270.32.19114View
Published (Version of record) Open Access

Abstract

Using defined elongation complexes formed on dC-tailed templates with Drosophila RNA polymerase II, we have examined elongation, pyrophosphorolysis, and DmS-II-mediated transcript cleavage and the inhibitory effect of alpha-amanitin on these processes. Analysis of pyrophosphorolysis on soluble or immobilized and templates confirmed that NTPs are liberated instead of dinucleotides that are released during DmS-II-mediated transcript cleavage. 10 microgram/ml alpha-amanitin completely inhibited DmS-II-mediated transcript cleavage but allowed extended pyrophosphorolysis and nucleotide addition to occur. alpha-Amanitin dramatically decreased the Vmax for nucleotide addition but only slightly affected the Km for nucleotides. Although the processes ae mechanistically distinct, both pyrophosphorolysis and DmS-II-mediated transcript cleavage frequently resulted in similar patterns of shortened transcript. Since polymerase molecules encounter similar kinetic barriers during both processes, it is possible that there is a common step in the reverse movement of the polymerase.

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