The Effect of Divalent Cations and Core Polymerase in the Abortive Initiation by Escherichia Coli Dna-Dependent Rna Polymerase Using Phosphonate Dinucleotide Primers

Abstract

The effect of divalent Mg²⁺ and Mn²⁺ cations on the elongation of ApU, UpA and their 3′-O- and 5′-O-phosphonylmethyl analogues by RNA polymerase holoenzyme to the corresponding trinucleo-tides on a poly(dA-dT) template was investigated. In contrast to Mg^z+ ions, Mn²⁺ ions enhance abortive trinucleotide synthesis. This effect is more pronounced with phosphonylmethyl analogues. The core enzyme cannot catalyze the elongation of either (2′-5′) UpA or phosphonylmethyl analogues. The localization of the divalent cation activator, as well as the role of the σ subunit at the catalytic centre of the holoenzyme, is discussed.

Key Words:

• Divalent cations
• Core polymerase
• Phosphonate dinucleotide primers