WHITE-COLLAR-2, A PARTNER IN BLUE-LIGHT SIGNAL-TRANSDUCTION, CONTROLLING EXPRESSION OF LIGHT-REGULATED GENES IN NEUROSPORA-CRASSA

A saturating genetic dissection of 'blind' mutants in Neurospora crass a has identified a total of two nonredundant loci (wc-1 and wc-2) each of which is required for blue-light perception/signal transduction. P reviously, we demonstrated that WC1 is a putative zinc finger transcri ption factor able to bind specifically to a light-regulated promoter. Here, we present the cloning and characterization of the wc-2 gene. We demonstrate using mutation analysis and in vitro DNA-binding assays t hat WC2, the second partner of this light signal transduction system, encodes a functional zinc finger DNA-binding protein with putative PAS dimerization and transcription activation domains. This molecular gen etic dissection of the second of two components of this light signal t ransduction system has enabled us to devise a model whereby WC1 and WC 2 are proposed to interact via homologous PAS domains, bind to promote rs of light-regulated genes and activate transcription. As such, this study provides the first insight into two co-operating partners in blu e-light signal transduction in any organism and describes the molecula r tools with which to dissect this enigmatic process.