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Biochem J. 2016 Jun 15;473(12):1733-44. doi: 10.1042/BCJ20160189. Epub 2016 Apr 8.

The epigenetic regulator Smchd1 contains a functional GHKL-type ATPase domain.

Author information

1
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
2
Biomolecular Interactions Centre and School of Biological Sciences, University of Canterbury, Christchurch 8042, New Zealand Bio21 Institute, Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
3
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
4
Biomolecular Interactions Centre and School of Biological Sciences, University of Canterbury, Christchurch 8042, New Zealand.
5
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia jamesm@wehi.edu.au.

Abstract

Structural maintenance of chromosomes flexible hinge domain containing 1 (Smchd1) is an epigenetic regulator that plays critical roles in gene regulation during development. Mutations in SMCHD1 were recently implicated in the pathogenesis of facioscapulohumeral muscular dystrophy (FSHD), although the mechanistic basis remains of outstanding interest. We have previously shown that Smchd1 associates with chromatin via its homodimeric C-terminal hinge domain, yet little is known about the function of the putative GHKL (gyrase, Hsp90, histidine kinase, MutL)-type ATPase domain at its N-terminus. To formally assess the structure and function of Smchd1's ATPase domain, we have generated recombinant proteins encompassing the predicted ATPase domain and the adjacent region. Here, we show that the Smchd1 N-terminal region exists as a monomer and adopts a conformation resembling that of monomeric full-length heat shock protein 90 (Hsp90) protein in solution, even though the two proteins share only ∼8% overall sequence identity. Despite being monomeric, the N-terminal region of Smchd1 exhibits ATPase activity, which can be antagonized by the reaction product, ADP, or the Hsp90 inhibitor, radicicol, at a nanomolar concentration. Interestingly, introduction of an analogous mutation to that identified in SMCHD1 of an FSHD patient compromised protein stability, suggesting a possible molecular basis for loss of protein function and pathogenesis. Together, these results reveal important structure-function characteristics of Smchd1 that may underpin its mechanistic action at the chromatin level.

KEYWORDS:

GHKL-ATPase; Hsp90; Smchd1

PMID:
27059856
DOI:
10.1042/BCJ20160189
[Indexed for MEDLINE]

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