RNA metabolism, manganese, and RNA polymerases of zinc-sufficient and zinc-deficient Euglena gracilis.

Abstract

The 3 major RNA classes from zinc-sufficient [(+Zn)] and zinc-deficient [(-Zn)] E. gracilis were separated by affinity chromatography on oligo(dT)- and N-{N''-[m-(dihydroxyboryl)phenyl]succinamoyl}aminoethyl (DBAE)-celluloses. The total RNA content and the ribosomal and tRNA fractions are the same in (+Zn) and (-Zn) cells. In (-Zn) cells, the mRNA fraction increases, and its altered base composition reveals additional bases and a 2-fold increase in the (G + C)/(A + U) ratio. Since the intracellular content of Mn increases in (-Zn) cells, its role in determining these changes in RNA composition was examined. An increase in the Mn2+ content from 1-10 mM in assays with RNA polymerases I and II from (+Zn) cells and those with the single RNA polymerase from (-Zn) cells decreases the ratio of UMP to CMP incorporated from 1.7-1.0, 2.1-0.8 and 3.5-0.4, respectively. Thus, Mn2+ concentration can significantly alter the products of the enzymatic action of RNA polymerases from both (+Zn) and (-Zn) E. gracilis cells.