The role of mRNA competition in regulating translation. II. Development of a quantitative in vitro assay.
Competition among excess mRNAs for a limiting, message-discriminatory initiation component (or set of components) has been studied in vitro. Procedures have been devised which provide maximum sensitivity with minimum potential for artifact. These procedures produce data that can be analyzed quantitatively to obtain numerical constants characteristic of a given mRNA's intrinsic initiation efficiency or, more precisely, competitive efficiency. A major advantage of this approach is that this information can be determined for individual mRNAs within a mixture of RNAs without the necessity of determining individual mRNA concentrations. The effects of potassium chloride concentration and magnesium acetate concentration on mRNA competitive efficiencies have been studied using these procedures.