Effects of divalent cations on the splicing of phage T4 thymidylate synthase intron RNA

Abstract

Effects of divalent cations such as Mg2+, Mn2+, Ca2+, and Zn2 on splicing activity of phage T4 thymidylate synthase intron RNA have been investigated. At the concentration of 0.5 mM Mn2+ in the absence of Mg2+, a very small amount of pre‐RNA was cleaved into ligation products (E1‐E2) but no circular or linear intron was produced. As the concentration of Mn2+ was increased from 1 to 5 mM. the pre‐RNA was completely hydrolyzed. In the presence of 5 mM Mg2+, both the linear intron and circular intron were produced but no E1‐E2 ligation product was produced. At both 3 and 5 mM Mn2+, the RNA was hydrolyzed completely as observed with no Mg2+ being present. In the case of Zn2+, even at 0.5 mM concentration, the pre‐RNA was completely hydrolyzed. This observation suggested that Zn2+ facilitates RNA hydrolysis more rapidly than Mn2+ does. At 5mM Ca2+, the RNA was not hydrolyzed and remained intact as a primary transcript.