The effect of divalent cations and core polymerase in the abortive initiation by escherichia coli dna-dependent rna polymerase using phosphonate dinucleotide primers

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.