The new paper published in Nucleic Acids Research advances this understanding by identifying a third, crucial player in this process: the glucocorticoid receptor (GR). The GR is a transcription factor belonging to the nuclear receptor superfamily, a group of proteins that respond to hormones and are essential for a wide array of cellular functions, from metabolism to immune response.
The researchers discovered that NIPBL does not work in isolation with MAU2. Instead, they form what is known as the NIPBL-MAU2-GR ternary complex. This discovery is a major leap forward in molecular biology, as it reveals a direct physical and functional link between a hormone receptor and the machinery that structures the genome.
"This NIPBL-MAU2-GR ternary complex modulates the transcription, since it facilitates the interaction of the glucocorticoid receptor (GR) with NIPBL and MAU2, which is the cohesion-loading factor," explain Alba Jiménez-Panizo and Andrea Alegre-Martí, researchers from IBUB and co-authors of the study. "When the GR interacts with these two proteins, it alters the structure of chromatin and affects the process of gene expression."
By facilitating this interaction, the complex ensures that the glucocorticoid receptor can effectively reach its target genes and initiate the necessary changes in DNA folding to activate them. This mechanism highlights the dynamic nature of the genome, where structural proteins and signaling molecules work in concert to translate environmental cues into biological action.
To reach these conclusions, the international team employed a suite of state-of-the-art techniques. This included advanced microscopic visualization capable of capturing real-time images of molecular complexes as they bind to chromatin within living cells. These observations were complemented by rigorous biochemical and biophysical analyses, allowing the researchers to view the NIPBL-MAU2-GR complex from both a structural and a cellular perspective.
Cornelia de Lange Syndrome and Cohesinopathies
The implications of this research extend far beyond basic biology, offering vital insights into a group of rare and often devastating conditions known as cohesinopathies. The most prominent among these is Cornelia de Lange syndrome (SCdL), a developmental disorder that affects many parts of the body. Individuals with SCdL often experience slow growth before and after birth, intellectual disabilities, and skeletal abnormalities affecting the arms and hands.
SCdL is primarily caused by mutations in the genes that encode the cohesin complex or its regulatory proteins, including NIPBL, SMC1A, HDAC8, RAD21, and SMC3. Another related condition, Roberts syndrome, also stems from similar genetic disruptions, leading to severe malformations during embryonic development.
