Roles in dimerization and blue light photoresponse of the PAS and LOV domains of Neurospora crassa white collar proteins

The genes coding for white collar-1 and white collar-2 (wc-1 and we-2) have been isolated previously, and their products characterized as Zn-finger transcription factors involved in the control of blue light-induced genes, Here, we show that the PAS dimerization domains present in both proteins enable the WC-1 and WC-2 proteins to dimerize in vitro, Homodimers and heterodimers are formed between the white collar (WC) proteins, A computer analysis of WC-1 reveals a second domain, called LOV, also identified in NPH1, a putative blue light photoreceptor in plants and conserved in redox-sensitive proteins and in the phytochromes, The WC-1 LOV domain does not dimerize with canonical PAS domains, but it is able to self-dimerize, The isolation of three blind wc-1 strains, each with a single amino acid substitution only in the LOV domain, reveals that this region is essential for blue light responses in Neurospora, The demonstration that the WC-1 proteins in these LOV mutants are still able to self-dimerize suggests that this domain plays an additional role, essential in blue light signal transduction.