Interpreting Notch signals: characterisation of dynamic transcription hubs by live imaging
type: CreativeWork
description: The Notch signalling pathway, crucial for development, activates upon cell-to-cell contact. Despite lacking any amplification, activation of target genes is achieved robustly and efficiently after contact-induced cleavage of the Notch transmembrane protein. How relatively few molecules of the activated, cleaved Notch achieve robust activation of genes is not well understood. Additionally, CSL, the Transcription Factor cleaved Notch interacts with, has relatively short DNA residence times, contrasting with a much longer duration of gene transcription. There are gaps in our understanding of how Notch activation results in transcription complex recruitment at gene regulatory regions and how this translates in the activation of target genes. A live imaging approach was taken to understand the mechanisms for robust activation of Notch targets, focusing on the co-activator Mastermind, a key component of the Notch transcription complex. Specifically, its enrichment and behaviour were characterised at a regulated gene locus in Notch active cells, enabling the study of a localised hub or condensate, and how it promotes transcription of target genes. First, analysis of Mastermind recruitment revealed that it forms dynamic transcription hubs in Notch active (Notch ON) cells. The proposed Notch hubs are formed by a combination of DNA-binding and interactions mediated by intrinsically disordered regions. Notably, Mastermind itself was not essential for hub formation as, when depleted, a modified hub persisted although transcription of Notch targets was lost. Factors that were involved in stabilising Mam were investigated, with CBP/p300 and the CDK8 module of the Mediator complex recruited to the transcription hub and required for transcription. However, of the two complexes, only the CDK8 module had an influence on Mam recruitment at the target locus. Further investigation suggested the enrichment of the CDK8 module and Mam in the transcription hub are interdependent. Second, to…
abstract: The Notch signalling pathway, crucial for development, activates upon cell-to-cell contact. Despite lacking any amplification, activation of target genes is achieved robustly and efficiently after contact-induced cleavage of the Notch transmembrane protein. How relatively few molecules of the activated, cleaved Notch achieve robust activation of genes is not well understood. Additionally, CSL, the Transcription Factor cleaved Notch interacts with, has relatively short DNA residence times, contrasting with a much longer duration of gene transcription. There are gaps in our understanding of how Notch activation results in transcription complex recruitment at gene regulatory regions and how this translates in the activation of target genes. A live imaging approach was taken to understand the mechanisms for robust activation of Notch targets, focusing on the co-activator Mastermind, a key component of the Notch transcription complex. Specifically, its enrichment and behaviour were characterised at a regulated gene locus in Notch active cells, enabling the study of a localised hub or condensate, and how it promotes transcription of target genes. First, analysis of Mastermind recruitment revealed that it forms dynamic transcription hubs in Notch active (Notch ON) cells. The proposed Notch hubs are formed by a combination of DNA-binding and interactions mediated by intrinsically disordered regions. Notably, Mastermind itself was not essential for hub formation as, when depleted, a modified hub persisted although transcription of Notch targets was lost. Factors that were involved in stabilising Mam were investigated, with CBP/p300 and the CDK8 module of the Mediator complex recruited to the transcription hub and required for transcription. However, of the two complexes, only the CDK8 module had an influence on Mam recruitment at the target locus. Further investigation suggested the enrichment of the CDK8 module and Mam in the transcription hub are interdependent. Second, to…
author: De Haro Arbona, Francisco Javier
language: eng
keywords: Notch signals, Transcription hubs, Drosophila, Transcription memory, MamRC, Mastermind
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/aeac97fb-667a-493f-a6ec-a73441afb4fa/download
license: http://purl.org/NET/rdflicense/allrightsreserved
date published: 2024-09-30
date modified: 2026-07-22T22:24:07Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.116485