Functional interaction between the small GTP-binding protein Rin and the N-terminal of Brn-3a transcription factor.

Brn-3a is a transcription factor belonging to the class IV of POU domain transcription factors. It is expressed throughout the peripheral nervous system but especially in postmitotic sensory neurons of dorsal root ganglia. Brn-3a is known to regulate different genes involved in neuronal differentiation and survival. It has been shown that some of these genes require the N-terminal domain of Brn-3a in order to be activated and this effect is observed only in neurons suggesting that it may require a neuronal-specific cofactor. In order to identify this putative factor(s) we screened a cDNA library via a variant of the original yeast two-hybrid system. By using the N-terminal of Brn-3a as the bait, we have repeatedly isolated a protein named Rin, an incompletely characterized small GTP-binding protein expressed only in neurons. In this work, we describe the evidence for a functional interaction between Brn-3a and Rin and demonstrate the role of Rin in modulating the activation of the Brn-3a regulated egr-1 promoter by the N-terminal domain of Brn-3a.