Changes in searching behaviour of CSL transcription complexes in Notch active conditions

Area of Science:

• Cellular and Molecular Biology
• Developmental Biology
• Gene Regulation

Background:

• Cell fate determination relies on external signals, including the Notch signaling pathway.
• The Notch pathway regulates target gene expression via the core transcription factor CSL.
• Understanding transcription factor dynamics is key to deciphering Notch-mediated transcriptional changes.

Purpose of the Study:

• To investigate the real-time behavior of the CSL transcription factor under Notch signaling.
• To elucidate how Notch activity influences CSL dynamics and target gene regulation.

Main Methods:

• In vivo Single Molecule Localisation Microscopy (SMLM) was employed to track CSL molecules.
• Trajectory analysis was used to quantify CSL binding and diffusion behaviors.

Main Results:

• Notch activation increases the fraction of bound CSL molecules.
• Notch-On conditions promote exploratory behaviors in CSL and its co-activator Mastermind.
• Both CSL and Mastermind exhibit local exploration near Notch target loci and other CSL clusters.

Conclusions:

• CSL adopts an exploratory behavior when part of the Notch activation complex.
• This exploratory behavior facilitates local searching and retention at target enhancers.
• The altered CSL dynamics explain its efficient occupancy increase at target sites under Notch-On conditions.