Analysis of nucleic acid binding by a recombinant translin-trax complex

Translin is a highly conserved mammalian RNA and DNA-binding protein involved in DNA recombination and RNA trafficking. Crystal structures of mouse and human translin have been solved, but do not provide information about nucleic acid binding or recognition. Translin has a partner protein, translin-associated factor x (trax), which is believed to regulate translin's subcellular locale and affinity for certain RNA and DNA sequences. Here we present a comparative study of recombinant translin and translin-trax complex binding to specific RNA and DNA sequences. It was observed that translin preferentially binds to G-rich RNA sequences whereas translin-trax preferentially binds G-rich DNA sequences. Translin can bind mRNA sequences with sub-micromolar Kd values, and the complex with trax can bind G-rich DNA with similar affinity. We conclude that trax acts to regulate translin's RNA and DNA binding affinities as part of a cellular RNA trafficking mechanism.