Nuclear factors which bind to Dictyostelium discoideum transfer RNA genes

RNA Polymerase III transcription factors from the cellular slime mold Dictyostelium discoideum were characterized, based on their stable binding to isolated tRNA genes. Different protein complexes are sequestered on DNA fragments containing tRNA genes depending on the conditions by which the nuclei were extracted. Binding specificity was determined through competition assays using competitor tRNA genes from the same gene family, from different gene families and from truncated tRNA genes. The complex with the highest multiformity of interdependent proteins is able to assemble with low affinity on a B-block-free tDNA template, whereas most lower molecular weight complexes require the presence of an intact B-block promoter element in order to assemble.