The B-WICH complex is a large 3 Mdalton complex containing SMARCA5 (SNF2H), BAZ1B (WSTF), ERCC6 (CSB), MYO1C (Nuclear myosin 1c) (Cavellan et al. 2006, Percipalle et al. 2006, Vintermist et al. 2001, Sarshad et al. 2013, Shen et al. 2013, reviewed in Percipalle and Farrants 2006, , SF3B1, DEK, MYBBP1A, and DDX21. B-WICH is found at active rRNA genes as well as at 5S rRNA and 7SL RNA genes. B-WICH appears to remodel chromatin and recruit histone acetyltransferases that modify histones to transcriptionally active states.
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Sarshad AA, Corcoran M, Al-Muzzaini B, Borgonovo-Brandter L, Von Euler A, Lamont D, Visa N, Percipalle P.; ''Glycogen synthase kinase (GSK) 3β phosphorylates and protects nuclear myosin 1c from proteasome-mediated degradation to activate rDNA transcription in early G1 cells.''; PubMedEurope PMCScholia
Comai L, Zomerdijk JC, Beckmann H, Zhou S, Admon A, Tjian R.; ''Reconstitution of transcription factor SL1: exclusive binding of TBP by SL1 or TFIID subunits.''; PubMedEurope PMCScholia
Russell J, Zomerdijk JC.; ''The RNA polymerase I transcription machinery.''; PubMedEurope PMCScholia
Comai L, Tanese N, Tjian R.; ''The TATA-binding protein and associated factors are integral components of the RNA polymerase I transcription factor, SL1.''; PubMedEurope PMCScholia
Philimonenko VV, Zhao J, Iben S, Dingová H, Kyselá K, Kahle M, Zentgraf H, Hofmann WA, de Lanerolle P, Hozák P, Grummt I.; ''Nuclear actin and myosin I are required for RNA polymerase I transcription.''; PubMedEurope PMCScholia
Cavellán E, Asp P, Percipalle P, Farrants AK.; ''The WSTF-SNF2h chromatin remodeling complex interacts with several nuclear proteins in transcription.''; PubMedEurope PMCScholia
Gorski JJ, Pathak S, Panov K, Kasciukovic T, Panova T, Russell J, Zomerdijk JC.; ''A novel TBP-associated factor of SL1 functions in RNA polymerase I transcription.''; PubMedEurope PMCScholia
Christiansen M, Thorslund T, Jochimsen B, Bohr VA, Stevnsner T.; ''The Cockayne syndrome group B protein is a functional dimer.''; PubMedEurope PMCScholia
Vintermist A, Böhm S, Sadeghifar F, Louvet E, Mansén A, Percipalle P, Ostlund Farrants AK.; ''The chromatin remodelling complex B-WICH changes the chromatin structure and recruits histone acetyl-transferases to active rRNA genes.''; PubMedEurope PMCScholia
Bell SP, Pikaard CS, Reeder RH, Tjian R.; ''Molecular mechanisms governing species-specific transcription of ribosomal RNA.''; PubMedEurope PMCScholia
Sarshad AA, Percipalle P.; ''New insight into role of myosin motors for activation of RNA polymerases.''; PubMedEurope PMCScholia
Shen M, Zhou T, Xie W, Ling T, Zhu Q, Zong L, Lyu G, Gao Q, Zhang F, Tao W.; ''The chromatin remodeling factor CSB recruits histone acetyltransferase PCAF to rRNA gene promoters in active state for transcription initiation.''; PubMedEurope PMCScholia
Pijnappel WP, Kolkman A, Baltissen MP, Heck AJ, Timmers HM.; ''Quantitative mass spectrometry of TATA binding protein-containing complexes and subunit phosphorylations during the cell cycle.''; PubMedEurope PMCScholia
Percipalle P, Fomproix N, Cavellán E, Voit R, Reimer G, Krüger T, Thyberg J, Scheer U, Grummt I, Farrants AK.; ''The chromatin remodelling complex WSTF-SNF2h interacts with nuclear myosin 1 and has a role in RNA polymerase I transcription.''; PubMedEurope PMCScholia
Sarshad A, Sadeghifar F, Louvet E, Mori R, Böhm S, Al-Muzzaini B, Vintermist A, Fomproix N, Östlund AK, Percipalle P.; ''Nuclear myosin 1c facilitates the chromatin modifications required to activate rRNA gene transcription and cell cycle progression.''; PubMedEurope PMCScholia
Percipalle P, Farrants AK.; ''Chromatin remodelling and transcription: be-WICHed by nuclear myosin 1.''; PubMedEurope PMCScholia
Direct interactions between BAZ1B (WSTF) and histone acetyltransferases KAT2B, KAT2A, and EP300 are weak (Vintermist et al. 2011) so the acetyltransferases may interact with other subunits of B‑WICH or with proteins not in the B‑WICH complex. The ERCC6 (CSB) component of B‑WICH and MYOIC interact with KAT2B (PCAF) (Sarshad et al. 2013, Shen et al. 2013). The histone acetyltransferases are believed to acetylate histone H3 at lysine‑9 in rDNA since this modification is reduced in WSTF and MYOIC knockdown cells (Vintermist et al. 2011, Sarshad et al. 2013). Knockdown of KAT2B causes loss of acetylation on histone H4 and on histone H3 at lysine‑9 (Shen et al. 2013).
Histone acetyltransferases recruited by the B‑WICH complex acetylate histone H3 at lysine‑9. Knockdown of the BAZ1B (WSTF) and MYOIC components of B‑WICH cause a loss of histone acetyltransferases KAT2B (PCAF), KAT2A (GCN5), and EP300 (p300) and a reduction of acetylated histone H3. Knockdown of KAT2B (PCAF) causes a reduction in acetylation of histone H3 at lysine‑9, leading to reduced rRNA synthesis levels (Sarshad et al. 2013, Shen et al. 2013).
Active rRNA genes are bound by the B‑WICH multiprotein complex (Cavellan et al. 2006, Percipalle et al. 2006). B-WICH binds the promoter region of the gene (Percipalle et al. 2006, Sarshad et al. 2013). The MYO1C component of the B-WICH complex binds chromatin and interacts with SMARCA5. Binding causes 200 bp of chromatin at the promoter to adopt a more open configuration and contributes to epigenetic modifications compatible with transcription activation (Vintermist et al. 2011, Sarshad et al. 2013). At the rRNA gene promoter the SMARCA5-MYOIC interaction is excluded when MYOIC interacts with actin in complex with RNA polymerase I (Sarshad et al. 2013). Binding of MYOIC to chromatin is regulated by GSK3beta-dependent phosphorylation that targets the MYOIC chromatin binding domain (Sarshad et al. 2014). Binding of MYOIC to the RNA polymerase I is partly mediated via phosphorylated TIF1A (Philimonenko et al. 2004). Binding of B‑WICH to rRNA genes requires MYOIC to be recruited to active rRNA genes and this mechanism appears to be a requirement to activate and maintain transcription by RNA polymerase I (Percipalle et al. 2006, Sarshad et al. 2013, Sarshad et al. 2014, reviewed in Sarshad and Percipalle 2014).
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Promoter:SL1:RNA
Pol IAnnotated Interactions
Promoter:SL1:RNA
Pol IPromoter:SL1:RNA
Pol I