Fungal CSL transcription factors
Martin Prevorovský1, Frantisek Půta, Petr Folk
1Department of Physiology and Developmental Biology, Faculty of Science, Charles University in Prague, Vinicná 7, Praha 2, Czech Republic. prevorov@natur.cuni.cz <prevorov@natur.cuni.cz>
Background:
The CSL (CBF1/RBP-Jkappa/Suppressor of Hairless/LAG-1) transcription factor family members are well-known components of the transmembrane receptor Notch signaling pathway, which plays a critical role in metazoan development. They function as context-dependent activators or repressors of transcription of their responsive genes, the promoters of which harbor the GTG(G/A)GAA consensus elements. Recently, several studies described Notch-independent activities of the CSL proteins.
Results:
We have identified putative CSL genes in several fungal species, showing that this family is not confined to metazoans. We have analyzed their sequence conservation and identified the presence of well-defined domains typical of genuine CSL proteins. Furthermore, we have shown that the candidate fungal protein sequences contain highly conserved regions known to be required for sequence-specific DNA binding in their metazoan counterparts. The phylogenetic analysis of the newly identified fungal CSL proteins revealed the existence of two distinct classes, both of which are present in all the species studied.
Conclusion:
Our findings support the evolutionary origin of the CSL transcription factor family in the last common ancestor of fungi and metazoans. We hypothesize that the ancestral CSL function involved DNA binding and Notch-independent regulation of transcription and that this function may still be shared, to a certain degree, by the present CSL family members from both fungi and metazoans.
Insights
The CSL (CBF1/RBP-Jkappa/Suppressor of Hairless/LAG-1) transcription factor family, known for its role in Notch signaling, is also found in fungi. These fungal CSL proteins likely retain ancestral DNA-binding and transcriptional regulatory functions.
Area of Science:
- Evolutionary biology
- Molecular biology
- Genetics
Background:
- CSL (CBF1/RBP-Jkappa/Suppressor of Hairless/LAG-1) proteins are key in metazoan Notch signaling.
- They act as context-dependent transcription regulators.
- Notch-independent CSL functions have recently been described.
Purpose of the Study:
- To investigate the presence and conservation of CSL genes outside of metazoans.
- To explore the evolutionary origins of the CSL transcription factor family.
- To understand the ancestral functions of CSL proteins.
Main Methods:
- Bioinformatic analysis of fungal genomes to identify CSL genes.
- Sequence conservation analysis of identified CSL proteins.
- Phylogenetic analysis of fungal and metazoan CSL proteins.
Main Results:
- Putative CSL genes were identified in several fungal species.
- Fungal CSL proteins possess conserved domains characteristic of genuine CSLs.
- Phylogenetic analysis revealed two distinct CSL classes in fungi, present across all studied species.
- Conserved regions for DNA binding were identified in fungal CSL candidates.
Conclusions:
- The CSL transcription factor family likely originated in the last common ancestor of fungi and metazoans.
- Ancestral CSL function probably involved DNA binding and Notch-independent transcriptional regulation.
- This ancestral function may be conserved to some extent in extant fungal and metazoan CSL proteins.
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