Biology subjects

Van Belle, S.

Publications and source records attributed to Van Belle, S..

3 recordsLinked to original sources

bioRxiv2024

LEDGF interacts with the NID of MeCP2 and modulates MeCP2 condensates

Methyl-CpG-binding protein 2 (MeCP2) is a ubiquitously expressed nuclear protein that is involved in transcriptional regulation and chromatin remodeling. MeCP2 exists in two isoforms, MeCP2 E1 and MeCP2 E2, which share the same functional domains. Loss-of-function mutations in the MeCP2 gene are the main cause of Rett syndrome (RTT). Previous studies identified a direct interaction between MeCP2 and Lens Epithelium-derived Growth Factor (LEDGF), a transcriptional regulator that also exists in two isoforms, LEDGF/p75 and LEDGF/p52. Here, we further characterized the molecular and functional interaction between MeCP2 and LEDGF. The NID domain in MeCP2 is crucial for the binding to the PWWP-CR1 region of LEDGF. Introduction of R306C, a known RTT mutation in the NID of MeCP2, reduced the interaction with LEDGF. Our data reveal mutual inhibition of MeCP2 and LEDGF multimerization due to overlapping binding sites. In line with this observation, LEDGF depletion resulted in enlarged MeCP2 and heterochromatin condensates in NIH3T3 cells. Unraveling the molecular interaction and functional impact of the MeCP2-LEDGF interaction will increase our understanding of RTT pathogenesis.

molecular biology↗

bioRxiv2024

HIV integrase compacts viral DNA into biphasic condensates

The human immunodeficiency virus (HIV) infects non-dividing cells and its genome must be compacted to enter the cell nucleus. Here, we show that the viral enzyme integrase (IN) compacts HIV DNA mimetics in vitro. Under physiological conditions, IN-compacted genomes are consistent in size with those found for pre-integration complexes in infected cells. Compaction occurs in two stages: first IN tetramers bridge DNA strands and assemble into "rosette" structures that consist of a nucleo-protein core and extruding bare DNA. In a second stage, the extruding DNA loops condense onto the rosette core to form a disordered and viscoelastic outer layer. Notably, the core complex is susceptible towards IN inhibitors, whereas the diffuse outer layer is not. Together, our data suggest that IN has a structural role in viral DNA compaction and raise the possibility to develop inhibitors that target IN-DNA interactions in disordered condensates. TeaserSingle-molecule studies demonstrate the mechanism, dynamics, and drug-susceptibility of viral genome compaction by HIV integrase.

biophysics↗

bioRxiv2022

BET-independent MLV integration is retargeted in vivo and selects distinct genomic elements for lymphomagenesis

Moloney murine leukemia virus (MLV) infects BALB/c mice and induces T-cell lymphoma in mice. Retroviral integration is mediated by the interaction of the MLV integrase (IN) with members of the bromodomain and extra-terminal motif (BET) protein family (BRD2, BRD3 and BRD4). Introduction of the W390A mutation in MLV IN abolishes BET interaction. Here we compared the replication of W390A MLV and WT MLV in adult BALB/c mice to study the role of BET proteins in replication, integration and tumorigenesis in vivo. Comparing WT and W390A MLV infection revealed similar viral loads in blood, thymus and spleen cells. Interestingly, W390A MLV integration was retargeted away from GC-enriched genomic regions. However, both WT MLV and W390A MLV developed T cell lymphoma after a similar latency represented by an enlarged thymus and spleen and multi-organ tumor infiltration. Integration site sequencing from splenic tumor cells revealed clonal expansion in all WT MLV- and W390A MLV-infected mice. However, the integration profile of W390A MLV and WT MLV differed significantly. Integrations were enriched in enhancers and promoters but compared to WT, W390A MLV integrated less frequently into enhancers and more into oncogene bodies, such as Notch1 and Ppp1r16b. We conclude that host factors direct MLV in vivo integration site selection. Although, BET proteins target WT MLV integration preferentially towards enhancers and promoters, insertional lymphomagenesis can occur independently from BET, likely due to the intrinsically strong enhancer/promoter of the MLV LTR.

microbiology↗