Phosphorylation of Williams Syndrome Transcription Factor by MAPK Induces a Switching between Two Distinct Chromatin Remodeling Complexes

Abstract

Changes in the environment of a cell precipitate extracellular signals and sequential cascades of protein modification and elicit nuclear transcriptional responses. However, the functional links between intracellular signaling-dependent gene regulation and epigenetic regulation by chromatin-modifying proteins within the nucleus are largely unknown. Here, we describe novel epigenetic regulation by MAPK cascades that modulate formation of an ATPdependent chromatin remodeling complex, WINAC (WSTF Including Nucleosome Assembly Complex), an SWI/SNF-type complex containing Williams syndrome transcription factor (WSTF). WSTF, a specific component of two chromatin remodeling complexes (SWI/SNF-type WINAC and ISWI-type WICH), was phosphorylated by the stimulation of MAPK cascades in vitro and in vivo. Ser-158 residue in the WAC (WSTF/Acf1/cbpq46) domain, located close to the N terminus of WSTF, was identified as a major phosphorylation target. Using biochemical analysis of a WSTF mutant (WSTF-S158A) stably expressing cell line, the phosphorylation of this residue (Ser-158) was found to be essential for maintaining the association between WSTF and core BAF complex components, thereby maintaining the ATPase activity of WINAC. WINAC-dependent transcriptional regulation of vitamin D receptor was consequently impaired by this WSTF mutation, but the recovery from DNA damage mediated by WICH was not impaired. Our results suggest that WSTF serves as a nuclear sensor of the extracellular signals to fine-tune the chromatin remodeling activity of WINAC. WINAC mediates a previously unknown MAPK-dependent step in epigenetic regulation, and this MAPK-dependent switching mechanism between the two functionally distinct WSTF-containing complexes might underlie the diverse functions of WSTF in various nuclear events.

WSTF does it all: a multifunctional protein in transcription, repair, and replicationThis paper is one of a selection of papers published in a Special Issue entitled 31st Annual International Asilomar Chromatin and Chromosomes Conference, and has undergone the Journal’s usual peer review process.

“…The WSTF protein has recently been shown to be a target of MAP kinases both in vitro and in vivo (Oya et al 2009). MAPK phosphorylates WSTF protein within the WAC domain at serine 158 (S158).…”

“…While WSTF exists in both the phosphorylated and unphosphorylated form in vivo , researchers have shown that an unphosphorylatable WSTF mutant (WSTF S158A) displays a significantly reduced affinity for other components of the WINAC chromatin remodeling complex. This mutation also results in reduced WINAC transactivation and repression activity in the breast cancer cell line MCF7 (Oya et al 2009). Interestingly, WSTF S158A does not disrupt the association with ISWI and appears not to alter survival of cultured mouse embryonic fibroblast (MEF) cells upon treatment with MMS.…”

“…This finding reveals a post-translational modification of WSTF that is important for WINAC assembly and function, but not for WICH (Figure 3). It is possible that a MAPK-dependent switch mechanism exists between WICH and WINAC assembly through the post-translational phosphorylation of the WSTF WAC domain, and that WINAC-dependent chromatin remodeling is at least partly under MAPK control (Oya et al 2009). It is intriguing that the WAC domain is essential for WSTF’s H2A.X kinase activity; it will be interesting to see whether S158 phosphorylation impacts the kinase activity of WSTF.…”

ATP-Dependent Chromatin Remodeling Complexes as Novel Targets for Cancer Therapy

“…5.2; Becker & Workman, 2013). Complexes in the SWI/SNF family include the large multisubunit BAF, PBAF, and WINAC complexes which function as coregulators of transcription, and they also aid in the repair of DNA damage (Oya et al, 2009; Wang et al, 1996). Remodeling reactions catalyzed by SWI/SNF family members include simple nucleosome sliding reactions, but they can include more dramatic reactions like creating DNA loops on the surface of nucleosomes or the eviction of H2A/H2B dimers from the nucleosome structure (Bowman, 2010).…”

The role of maintenance proteins in the preservation of epithelial cell identity during mammary gland remodeling and breast cancer initiation

“…However, the most common cancer-related changes in the SWI/SNF complex are the loss or inactivation of the BRG1 or BRM subunit, which occur in a variety of tumors, including breast cancer[80],[81]. The genetic or epigenetic silencing of the BRG1 subunit is of particular relevance considering that, in addition to the BAF/PBAF complexes, BRG1 is the pivotal component in several other chromatin-remodeling and histone-modifying enzyme complexes, including the Williams syndrome transcription factor (WSTF)-including nucleosome assembly complex (WINAC), N-CoR, nucleosomal methylation activation complex (NUMAC), and mSin3A/histone deacetylase (HDAC) complex[82]–[84] ( Figure 3 ). In particular, when associated with coactivator-associated arginine methyltransferase-1 (CARM1) to form the NUMAC complex, BRG1 can recruit nuclear hormone receptors to EREs and cooperatively activate estrogen-dependent gene transcription[85]–[87].…”