The preRC protein ORCA organizes heterochromatin by assembling histone H3 lysine 9 methyltransferases on chromatin
Sumanprava Giri,
Vasudha Aggarwal,
Julien Pontis,
Zhen Shen,
Arindam Chakraborty,
Abid Khan,
Craig Mizzen,
Kannanganattu V Prasanth,
Slimane Ait-Si-Ali,
Taekjip Ha,
Supriya G Prasanth
Affiliations
Sumanprava Giri
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Vasudha Aggarwal
Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Julien Pontis
Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Epigénétique et Destin Cellulaire, UMR7216, Centre National de la Recherche Scientifique, Paris, France
Zhen Shen
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Arindam Chakraborty
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Abid Khan
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Craig Mizzen
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Kannanganattu V Prasanth
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Slimane Ait-Si-Ali
Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Epigénétique et Destin Cellulaire, UMR7216, Centre National de la Recherche Scientifique, Paris, France
Taekjip Ha
Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Champaign, United States; Department of Physics, Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Champaign, United States
Supriya G Prasanth
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Champaign, United States
Heterochromatic domains are enriched with repressive histone marks, including histone H3 lysine 9 methylation, written by lysine methyltransferases (KMTs). The pre-replication complex protein, origin recognition complex-associated (ORCA/LRWD1), preferentially localizes to heterochromatic regions in post-replicated cells. Its role in heterochromatin organization remained elusive. ORCA recognizes methylated H3K9 marks and interacts with repressive KMTs, including G9a/GLP and Suv39H1 in a chromatin context-dependent manner. Single-molecule pull-down assays demonstrate that ORCA-ORC (Origin Recognition Complex) and multiple H3K9 KMTs exist in a single complex and that ORCA stabilizes H3K9 KMT complex. Cells lacking ORCA show alterations in chromatin architecture, with significantly reduced H3K9 di- and tri-methylation at specific chromatin sites. Changes in heterochromatin structure due to loss of ORCA affect replication timing, preferentially at the late-replicating regions. We demonstrate that ORCA acts as a scaffold for the establishment of H3K9 KMT complex and its association and activity at specific chromatin sites is crucial for the organization of heterochromatin structure.
