Remodeling machines play an essential role in the control of gene expression, but how their activity is regulated is not known. Here we report that the nuclear protein nucleolin possesses a histone chaperone activity and that this factor greatly enhances the activity of the chromatin remodeling machineries SWI/SNF and ACF. Interestingly, nucleolin is able to induce the remodeling by SWI/SNF of macroH2A, but not of H2ABbd nucleosomes, which are otherwise resistant to remodeling. This new histone chaperone promotes the destabilization of the histone octamer, helping the dissociation of a H2A-H2B dimer, and stimulates the SWI/SNF-mediated transfer of H2A-H2B dimers. Furthermore, nucleolin facilitates transcription through the nucleosome, which is reminiscent of the activity of the FACT complex. This work defines new functions for histone chaperones in chromatin remodeling and regulation of transcription and explains how nucleolin could act on transcription.

Background: Cohesion of interendothelial junctions is maintained by the connections existing between the VE-cadherin⅐catenin complex and the actin cytoskeleton. Results: By interacting with ␣-catenin, the actin-binding protein EPLIN (epithelial protein lost in neoplasm) facilitates the recruitment of vinculin. Conclusion:The EPLIN␣-catenin link provides a mechanosensory machinery by acting as a tension transmitter. Significance: By anchoring the VE-cadherin⅐catenin complex to F-actin, EPLIN strengthens interendothelial junctions.