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| SWR1 | |
|---|---|
| Name | SWR1 |
| Type | Protein complex |
| Organism | Saccharomyces cerevisiae (originally) |
| Function | Chromatin remodeling, histone exchange |
| Subunits | Multiple (see Structure and Subunits) |
| Discovery | 1990s–2000s |
SWR1 SWR1 is a multisubunit chromatin remodeling complex first characterized in Saccharomyces cerevisiae and linked to histone variant exchange, DNA repair, transcriptional regulation, and genome stability. It is studied across model organisms including Schizosaccharomyces pombe, Drosophila melanogaster, Arabidopsis thaliana, and mammals such as Mus musculus and Homo sapiens, and it connects to pathways investigated by groups at institutions like Cold Spring Harbor Laboratory, Howard Hughes Medical Institute, and Max Planck Society.
SWR1 was identified through biochemical purification and genetic screens alongside complexes such as SWI/SNF and INO80 in yeast, and its activity was linked to incorporation of the histone variant H2A.Z at promoters, enhancers, and centromeres, complementary to work on RNA polymerase II, Mediator (coactivator complex), and TATA-binding protein. Studies using techniques developed at EMBL, European Molecular Biology Laboratory, and National Institutes of Health combined chromatin immunoprecipitation with mass spectrometry methods refined by teams at University of California, Berkeley, MIT, and Stanford University to map SWR1-dependent loci and to contrast SWR1 with remodelers characterized by Roger Kornberg and Peter Becker.
The SWR1 complex comprises a central ATPase related to the AAA+ family and many accessory subunits homologous to proteins in the SWR1 family of remodelers; core components include an ATPase paralogous to enzymes found in INO80 and SWI/SNF, plus actin-related proteins homologous to ACT1 and ARP4, HSA-domain proteins resembling factors studied by groups at EMBL-EBI and Wellcome Trust Sanger Institute, and YEATS- or bromodomain-containing proteins reminiscent of factors characterized in BRD4 research. Comparative proteomics linked SWR1 subunits to orthologs in SRCAP (SNF2-related CBP activator protein), Yaf9, Swc2, Swc5, Swc6, and Swc7, as well as to components analyzed by structural biology teams at Max Planck Institute for Biophysical Chemistry and Rutherford Appleton Laboratory.
SWR1 uses ATP hydrolysis to catalyze replacement of nucleosomal H2A with the variant H2A.Z, a process elucidated with single-molecule assays developed at Caltech and cryo-electron microscopy advances from Cryo-EM Facility, EMPIAR that paralleled structural solutions for ribosome and nucleosome complexes. Mechanistic parallels were drawn to ATP-dependent translocases worked on by Thomas Cech and Carol Greider laboratories, while kinetic and thermodynamic measurements leveraged methods from groups at Harvard Medical School and Yale University to define steps of DNA unwrapping, DNA tracking, and histone dimer eviction and deposition. Mutational analyses compared SWR1 ATPase motifs with those in Rad54 and SMARCA4, and crosslinking mass spectrometry connected substrate recognition to histone chaperones studied alongside Nap1 and FACT.
SWR1-mediated H2A.Z deposition influences transcriptional initiation at promoters regulated by factors such as Gal4, Gcn4, and Ssn6-Tup1, and it modulates chromatin boundary elements and silencing at loci regulated by Sir2, Sir3, and Sir4. Roles in DNA damage response link SWR1 to pathways involving Rad51, Mre11-Rad50-Nbs1 (MRN complex), Ku70/80, and double-strand break repair machines characterized by groups at European Molecular Biology Laboratory and Cold Spring Harbor Laboratory. In development and cell differentiation, SWR1 orthologs impact processes investigated in Drosophila melanogaster imaginal disc patterning, Arabidopsis thaliana flowering time regulated by FLOWERING LOCUS C, and mammalian stem cell programs involving Oct4, Sox2, and Nanog.
SWR1 activity is regulated by post-translational modifications of histones studied by labs at Medical Research Council, including acetylation by complexes containing Gcn5, methylation by Set1 and Set2, ubiquitylation pathways involving Rad6-Bre1, and phosphorylation events coordinated with kinases like Cyclin-dependent kinase 9 and ATM. Protein–protein interactions connect SWR1 to histone chaperones such as Nap1 and Asf1, to transcription factors like Rap1 and Cbf1, and to chromatin boundary factors such as CTCF in metazoans, with regulatory crosstalk probed by consortia including ENCODE and collaborations at Broad Institute.
Dysfunction of SWR1 orthologs and H2A.Z misregulation has been implicated in human diseases explored by clinical genetics groups at Dana-Farber Cancer Institute, Memorial Sloan Kettering Cancer Center, and National Cancer Institute, including cancer types where chromatin remodeler mutations co-occur with alterations in TP53, BRCA1, and PIK3CA. SWR1-related factors like SRCAP have been linked to syndromes studied by clinical teams at Mayo Clinic and Johns Hopkins Hospital, and SWR1 mechanisms are targeted in chemical biology efforts at Novartis and GlaxoSmithKline to develop epigenetic therapies analogous to inhibitors of EZH2 and HDACs. Research tools such as genome-wide CRISPR screens pioneered at Broad Institute, single-cell transcriptomics approaches from Sanger Institute, and advanced imaging developed at Max Planck Institute for Molecular Cell Biology and Genetics continue to expand understanding of SWR1 functions in health and disease.
Category:Chromatin remodeling complexes