Role of a white collar-1-white collar-2 complex in blue-light signal transduction.
Mutations in either white collar-1 (wc-1) or white collar-2 (wc-2) lead to a loss of most blue-light-induced phenomena in Neurospora crassa. Sequence analysis and in vitro experiments show that WC-1 and WC-2 are transcription factors regulating the expression of light-induced genes. The WC proteins form homo- and heterodimers in vitro; this interaction could represent a fundamental step in the control of their activity. We demonstrate in vivo that the WC proteins are assembled in a white collar complex (WCC) and that WC-1 undergoes a change in mobility due to light-induced phosphorylation events. The phosphorylation level increases progressively upon light exposure, producing a hyperphosphorylated form that is degraded and apparently replaced in the complex by a newly synthesized WC-1. WC-2 is unmodified and also does not change quantitatively in the time frame examined. Light-dependent phosphorylation of WC-1 also occurs in a wc-2 mutant, suggesting that a functional WC-2 is dispensable for this light-specific event. These results suggest that light-induced phosphorylation and degradation of WC-1 could play a role in the transient expression of blue-light-regulated genes. Our findings suggest a mechanism by which WC-1 and WC-2 mediate light responses in Neurospora.
Talora
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Dipartimento di Biotecnologie Cellulari Ed Ematologia, Sezione di Genetica Molecolare, Universita' di Roma 'La Sapienza', Policlinico Umberto I, Viale Regina Elena 32, 00161 Rome, Italy.
Franchi
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Linden
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Ballario
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Macino
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D000818:Animals; D000908:Antibodies, Fungal; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D019281:Dimerization; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000528:radiation effects; D005800:Genes, Fungal; D008027:Light; D046911:Macromolecular Substances; D008954:Models, Biological; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D010766:Phosphorylation; D011817:Rabbits; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D000908:Antibodies, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D046911:Macromolecular Substances; D014157:Transcription Factors; C105589:wc-1 protein, Neurospora crassa; C103772:white collar 2 protein, Neurospora