title: The cohesin-associated protein Wapal is required for proper Polycomb-mediated gene silencing.
abstract: BACKGROUND
  The cohesin complex consists of multiple core subunits that play critical roles in mitosis and transcriptional regulation. The cohesin-associated protein Wapal plays a central role in off-loading cohesin to facilitate sister chromatid separation, but its role in regulating mammalian gene expression is not understood. We used embryonic stem cells as a model, given that the well-defined transcriptional regulatory circuits were established through master transcription factors and epigenetic pathways that regulate their ability to maintain a pluripotent state.
  
  
  RESULTS
  RNAi-mediated depletion of Wapal causes a loss of pluripotency, phenocopying loss of core cohesin subunits. Using chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq), we determine that Wapal occupies genomic sites distal to genes in combination with CTCF and core cohesin subunits such as Rad21. Interestingly, genomic sites occupied by Wapal appear enriched for cohesin, implying that Wapal does not off-load cohesin at regions it occupies. Wapal depletion induces derepression of Polycomb group (PcG) target genes without altering total levels of Polycomb-mediated histone modifications, implying that PcG enzymatic activity is preserved. By integrating ChIP-seq and gene expression changes data, we identify that Wapal binding is enriched at the promoters of PcG-silenced genes and is required for proper Polycomb repressive complex 2 (PRC2) recruitment. Lastly, we demonstrate that Wapal is required for the interaction of a distal cis-regulatory element (CRE) with the c-Fos promoter.
  
  
  CONCLUSIONS
  Collectively, this work indicates that Wapal plays a critical role in silencing of PcG target genes through the interaction of distal CREs with promoters.
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, 8727 West Watertown Plank Road, Milwaukee, WI 53226 USA.
authors.forename: Cary
authors.initials: C
authors.lastname: Stelloh
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, 8727 West Watertown Plank Road, Milwaukee, WI 53226 USA.|Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Reimer
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, 8727 West Watertown Plank Road, Milwaukee, WI 53226 USA.
authors.forename: Kirthi
authors.initials: K
authors.lastname: Pulakanti
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, 8727 West Watertown Plank Road, Milwaukee, WI 53226 USA.|Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Blinka
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, 8727 West Watertown Plank Road, Milwaukee, WI 53226 USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Peterson
authors.affiliation: Dana Farber Cancer Institute, Harvard School of Public Health, Boston, MA USA.
authors.forename: Luca
authors.initials: L
authors.lastname: Pinello
authors.affiliation: Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI USA.
authors.forename: Shuang
authors.initials: S
authors.lastname: Jia
authors.affiliation: Department of Pediatrics, Massachusetts General Hospital, Boston, MA USA.
authors.forename: Sergei
authors.initials: S
authors.lastname: Roumiantsev
authors.affiliation: Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI USA.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Hessner
authors.affiliation: Sanford Research Center, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Milanovich
authors.affiliation: Dana Farber Cancer Institute, Harvard School of Public Health, Boston, MA USA.
authors.forename: Guo-Cheng
authors.initials: GC
authors.lastname: Yuan
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, 8727 West Watertown Plank Road, Milwaukee, WI 53226 USA.|Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI USA.|Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI USA.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Rao
keywords: Cohesin complex; Embryonic stem cells; Epigenetics; Polycomb complex; Wapal