Methods in Molecular Biology • 16 Enzymes of Molecular Biology

CHAPTER 5

Eukaryotic Nuclear RNA Polymerases

(EC 2.7.7.6)

Deborah tL Cook and Robert J. Slater

1. Introduction
   DNA-dependent RNA polymerases (ribonucleoside triphosphate:
   RNA nucleotidyltransferase, EC 2.7.7.6) catalyze the synthesis of RNA
   from ribonucleoside triphosphates in the presence of a DNA template
   and divalent cation (1).

ATP
CTP
GTP
UTP n

Mg 2+ or Mn 2÷

RNA + (PPi) n
DNA template
DNA-dependent RNA polymerase
The RNA molecules are synthesized complementary and antiparal-
lel to one of the DNA strands in a 5' to 3' direction. The ribonucleotides
are covalentlyjoined together by internucleoside 3'to 5' phosphodiester
bonds with concomitant release of inorganic pyrophosphate.
In order for the polymerase to do this, it must "recognize" the beginning
of the DNA sequence to be transcribed within the double-stranded
template; insert the correct nucleotide residue into each position, as
determined by the template sequence; carry out synthesis, so that RNA
is synthesized from beginning to end as a consequence of one poly-
merase binding event; and recognize termination signals in order to
end RNA synthesis at the appropriate point. To achieve all this, the
polymerase must be able to recognize regulatory sites on the DNA

From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology

Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

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