Abstract
Pontin/RUVBL1 and Reptin/RUVBL2 are DNA-dependent ATPases involved in numerous cellular processes and are essential components of chromatin remodeling complexes and transcription factor assemblies. However, their existence as monomeric and oligomeric forms with differential activity in vivo reflects their versatility. Using a biochemical approach, we have studied the role of the nucleosome core particle and histone N-terminal tail modifications in the assembly and enzymatic activities of Reptin/Pontin. We demonstrate that purified Reptin and Pontin form stable complexes with nucleosomes. The ATPase activity of Reptin/Pontin is modulated by acetylation and methylation of the histone H3 N terminus. In vivo, association of Reptin with the progesterone receptor gene promoter is concomitant with changes in H3 marks of the surrounding nucleosomes. Furthermore, the presence of H3 tail peptides regulates the monomer-oligomer transition of Reptin/Pontin. Proteins that are pulled down by monomeric Reptin/Pontin differ from those that can bind to hexamers. We propose that changes in the oligomeric status of Reptin/Pontin create a platform that brings specific cofactors close to gene promoters and loads regulatory factors to establish an active state of chromatin.
Highlights
Pontin and Reptin are main components of remodeling complexes responsible for chromatin dynamics
Electrophoretic mobility gel shift assays showed that Reptin or Pontin monomers form complexes with nucleosome-DNA substrates (Fig. 1, C and D, lanes 1– 4) in the same range of protein concentrations needed for binding to naked DNA (Fig. 1, C and D, lanes 13–16)
We provide evidence for physical interaction and functional interplay between Reptin/Pontin and chromatin
Summary
Pontin and Reptin are main components of remodeling complexes responsible for chromatin dynamics. Results: These ATPases interact with the chromatin basic unit, the nucleosome, which regulates Pontin/Reptin enzymatic activities and oligomerization assemblies. Pontin/RUVBL1 and Reptin/RUVBL2 are DNA-dependent ATPases involved in numerous cellular processes and are essential components of chromatin remodeling complexes and transcription factor assemblies. Their existence as monomeric and oligomeric forms with differential activity in vivo reflects their versatility. We report here our investigation of how the biochemical properties of monomers and oligomers of the Reptin/Pontin proteins contribute to the function of chromatin remodeling complexes through regulation of DNA binding. Reptin/Pontin conformational transitions arising from these interactions may coordinate recruitment of different protein partners
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