BZIP transcription factors and transcriptional regulatory networks in the neurospora circadian system.

Transcription factors lie at the core of gene regulatory networks and their interactions with cis-regulatory modules contribute to the precise regulation of gene expression. Circadian clocks control daily rhythms in gene expression in several organisms. The ascomycete Neurospora crassa has one of the best-understood circadian systems and a wealth of knowledge has accumulated on the molecular basis of its pacemaker. How the information is transmitted out of the oscillator to control overt rhythms however, is largely unknown. In addition, despite decades as a research model organism, little is known about transcriptional regulatory networks in this fungus and the vast majority of its transcription factors remain uncharacterized.

In an effort to improve current knowledge of output pathways in a clock model system and study transcriptional regulatory networks in a model eukaryote, we set out to characterize the bZIP family of transcriptional regulators in Neurospora, in the context of its circadian system. We identified novel bZIP proteins and through the use of a luciferase-based high-throughput screening system, we show that the expression of many of these regulators is controlled by the circadian clock. Further, we show that members of this family can regulate output pathways. Additionally, we report that MAPK and interestingly, cell fusion pathways mediate their rhythmic gene expression. To characterize regulatory networks in which these and all Neurospora transcription factors may participate, we used protein binding microarrays to examine their DNA binding specificities. This resulted in the determination of the sequence preference of over half of Neurospora transcription factors.

This is the first study aimed at studying sequence specificities on a global scale within the filamentous fungi. Such data resulted in the identification of the first ever transcription factor shown to be required for growth under osmotic stress in Neurospora. As a whole, the work reported on this study, represents a major advancement in the study of bZIP proteins and transcriptional regulatory networks in Neurospora.

• Nombre: Alejandro Montenegro Montero
• Laboratorio: Cronobiología
• Mención: Genética Molecular y Microbiología
• Director Tesis: Luis Larrondo