Biomedical subjects

Karine Lapouge

Publications and source records attributed to Karine Lapouge.

4 recordsLinked to original sources

PubMed2026

Molecular co-accessibility identifies coordinated regulation between distant cis-regulatory elements.

In metazoans, gene expression is typically regulated by a cis-regulatory landscape (CRL) composed of a promoter and multiple enhancers. How these cis-regulatory elements (CREs) coordinate their function across large genomic distances remains unclear. For example, is the simultaneous activation of multiple enhancers required to promote transcription? Here, we combined single-molecule footprinting with long-read sequencing to quantify how often chromatin accessibility and transcription factor binding co-occur across entire CRLs in the Drosophila genome. Analysis of thousands of individual DNA molecules at each locus revealed that CREs form a specific network with shared single-molecule chromatin accessibility profiles. Co-accessibility is not limited to adjacent CREs and is frequently observed between CREs brought into proximity by chromatin looping. Co-accessible CREs exhibit strong coordination in their cell-type-specific accessibility, linking enhancer activity with transcriptional activation. Our data uncover dependencies between CREs genome-wide and suggest that coordinated enhancer activation is a widespread mechanism regulating gene expression.

Animals↗

PubMed2006

New insights into the molecular basis of desmoplakin- and desmin-related cardiomyopathies.

Desmosomes are intercellular adhesive complexes that anchor the intermediate filament cytoskeleton to the cell membrane in epithelia and cardiac muscle cells. The desmosomal component desmoplakin plays a key role in tethering various intermediate filament networks through its C-terminal plakin repeat domain. To gain better insight into the cytoskeletal organization of cardiomyocytes, we investigated the association of desmoplakin with desmin by cell transfection, yeast two-hybrid, and/or in vitro binding assays. The results indicate that the association of desmoplakin with desmin depends on sequences within the linker region and C-terminal extremity of desmoplakin, where the B and C subdomains contribute to efficient binding; a potentially phosphorylatable serine residue in the C-terminal extremity of desmoplakin affects its association with desmin; the interaction of desmoplakin with non-filamentous desmin requires sequences contained within the desmin C-terminal rod portion and tail domain in yeast, whereas in in vitro binding studies the desmin tail is dispensable for association; and mutations in either the C-terminus of desmoplakin or the desmin tail linked to inherited cardiomyopathy seem to impair desmoplakindesmin interaction. These studies increase our understanding of desmoplakin-intermediate filament interactions, which are important for maintenance of cytoarchitecture in cardiomyocytes, and give new insights into the molecular basis of desmoplakin- and desmin-related human diseases.

Animals↗

PubMed2003

Molecular basis of phosphorylation-induced activation of the NADPH oxidase.

The multi-subunit NADPH oxidase complex plays a crucial role in host defense against microbial infection through the production of reactive oxygen species. Activation of the NADPH oxidase requires the targeting of a cytoplasmic p40-p47-p67(phox) complex to the membrane bound heterodimeric p22-gp91(phox) flavocytochrome. This interaction is prevented in the resting state due to an auto-inhibited conformation of p47(phox). The X-ray structure of the auto-inhibited form of p47(phox) reveals that tandem SH3 domains function together to maintain the cytoplasmic complex in an inactive form. Further structural and biochemical data show that phosphorylation of p47(phox) activates a molecular switch that relieves the inhibitory intramolecular interaction. This permits p47(phox) to interact with the cytoplasmic tail of p22(phox) and initiate formation of the active, membrane bound enzyme complex.

Amino Acid Sequence↗

PubMed2002

Architecture of the p40-p47-p67phox complex in the resting state of the NADPH oxidase. A central role for p67phox.

The phagocyte NADPH oxidase is a multiprotein enzyme whose subunits are partitioned between the cytosol and plasma membrane in resting cells. Upon exposure to appropriate stimuli multiple phosphorylation events in the cytosolic components take place, which induce rearrangements in a number of protein-protein interactions, ultimately leading to translocation of the cytoplasmic complex to the membrane. To understand the molecular mechanisms that underlie the assembly and activation process we have carried out a detailed study of the protein-protein interactions that occur in the p40-p47-p67(phox) complex of the resting oxidase. Here we show that this complex contains one copy of each protein, which assembles to form a heterotrimeric complex. The apparent high molecular weight of this complex, as observed by gel filtration studies, is due to an extended, non-globular shape rather than to the presence of multiple copies of any of the proteins. Isothermal titration calorimetry measurements of the interactions between the individual components of this complex demonstrate that p67(phox) is the primary binding partner of p47(phox) in the resting state. These findings, in combination with earlier reports, allow us to propose a model for the architecture of the resting complex in which p67(phox) acts as the bridging molecule that connects p40(phox) and p47(phox).

Amino Acid Motifs↗