Prothymosin alpha is a nonspecific facilitator of nuclear processes: Studies of run-on transcription

The effect of prothymosin a on transcriptional elongation has been examined . The addition of prothymosin a to COS-l and NIH3T3 cell nuclei engaged in run-on transcription stimulated RNA synthesis approximately two- to threefo ld in a dose-dependent manner. Polyglutamic acid or a random polypeptide co mposed of glutamic acid, alanine, and tyrosine, did not substitute for prot hymosin a. Enhanced transcription occurred in the presence of high and low doses of actinomycin D and in the presence of cu-amanitin, but not in nucle ar extracts. The stimulatory effect was dependent on a limiting concentrati on of one nucleoside triphosphate and was nearly abrogated by saturating le vels of precursors. In the presence of Sarkosyl, which itself increases tra nscription, prothymosin a was almost ineffectual. The data are consistent w ith a model in which prothymosin a does not interact directly with polymera ses but, instead, nonspecifically decreases the barriers to diffusion of ch arged molecules in electrostatically charged environments.