Structure-function analysis of mouse Sry reveals dual essential roles of the C-terminal polyglutamine tract in sex determination

Zhao, Liang, Ng, Ee Ting, Davidson, Tara-Lynne, Longmuss, Enya, Urschitz, Johann, Elston, Marlee, Moisyadi, Stefan, Bowles, Josephine and Koopman, Peter (2014) Structure-function analysis of mouse Sry reveals dual essential roles of the C-terminal polyglutamine tract in sex determination. Proceedings of the National Academy of Sciences, 111 32: 11768-11773. doi:10.1073/pnas.1400666111


Author Zhao, Liang
Ng, Ee Ting
Davidson, Tara-Lynne
Longmuss, Enya
Urschitz, Johann
Elston, Marlee
Moisyadi, Stefan
Bowles, Josephine
Koopman, Peter
Title Structure-function analysis of mouse Sry reveals dual essential roles of the C-terminal polyglutamine tract in sex determination
Journal name Proceedings of the National Academy of Sciences   Check publisher's open access policy
ISSN 0027-8424
1091-6490
Publication date 2014-08-12
Year available 2014
Sub-type Article (original research)
DOI 10.1073/pnas.1400666111
Open Access Status DOI
Volume 111
Issue 32
Start page 11768
End page 11773
Total pages 6
Editor Patricia K. Donahoe
Place of publication Washington, DC, United States
Publisher National Academy of Sciences
Language eng
Abstract The mammalian sex-determining factor SRY comprises a conserved high-mobility group (HMG) box DNA-binding domain and poorly conserved regions outside the HMG box. Mouse Sry is unusual in that it includes a C-terminal polyglutamine (polyQ) tract that is absent in nonrodent SRY proteins, and yet, paradoxically, is essential for male sex determination. To dissect the molecular functions of this domain, we generated a series of Sry mutants, and studied their biochemical properties in cell lines and transgenic mouse embryos. Sry protein lacking the polyQ domain was unstable, due to proteasomal degradation. Replacing this domain with irrelevant sequences stabilized the protein but failed to restore Sry's ability to up-regulate its key target gene SRY-box 9 (Sox9) and its sex-determining function in vivo. These functions were restored only when a VP16 transactivation domain was substituted. We conclude that the polyQ domain has important roles in protein stabilization and transcriptional activation, both of which are essential for male sex determination in mice. Our data disprove the hypothesis that the conserved HMG box domain is the only functional domain of Sry, and highlight an evolutionary paradox whereby mouse Sry has evolved a novel bifunctional module to activate Sox9 directly, whereas SRY proteins in other taxa, including humans, seem to lack this ability, presumably making them dependent on partner proteins(s) to provide this function.
Formatted abstract
The mammalian sex-determining factor SRY comprises a conserved high-mobility group (HMG) box DNA-binding domain and poorly conserved regions outside the HMG box. Mouse Sry is unusual in that it includes a C-terminal polyglutamine (polyQ) tract that is absent in nonrodent SRY proteins, and yet, paradoxically, is essential for male sex determination. To dissect the molecular functions of this domain, we generated a series of Sry mutants, and studied their biochemical properties in cell lines and transgenic mouse embryos. Sry protein lacking the polyQ domain was unstable, due to proteasomal degradation. Replacing this domain with irrelevant sequences stabilized the protein but failed to restore Sry’s ability to up-regulate its key target gene SRY-box 9 (Sox9) and its sex-determining function in vivo. These functions were restored only when a VP16 transactivation domain was substituted. We conclude that the polyQ domain has important roles in protein stabilization and transcriptional activation, both of which are essential for male sex determination in mice. Our data disprove the hypothesis that the conserved HMG box domain is the only functional domain of Sry, and highlight an evolutionary paradox whereby mouse Sry has evolved a novel bifunctional module to activate Sox9 directly, whereas SRY proteins in other taxa, including humans, seem to lack this ability, presumably making them dependent on partner proteins(s) to provide this function.

Significance:
The sex-determining factor SRY is thought to function by up-regulating expression of its key target gene SRY-box 9 (SOX9) in pre-Sertoli cells of the developing gonads, but evidence for a transactivation domain is lacking for human SRY and is limited to in vitro evidence for mouse Sry. The latter is unusual in possessing a polyglutamine tract at its C terminus. We demonstrate, using a combination of biochemical, cell-based, and transgenic mouse assays, that this domain plays essential roles in both protein stabilization and transactivation of Sox9, and is required for male sex determination in mice. Our data indicate that mouse Sry has evolved a novel bifunctional module, revealing an unexpected level of plasticity of sex-determining mechanisms even among mammals.
Keyword Sex development
Y chromosome
Testis
TESCO
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2015 Collection
Institute for Molecular Bioscience - Publications
 
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Created: Sat, 02 Aug 2014, 01:26:49 EST by Susan Allen on behalf of Institute for Molecular Bioscience