title: Defective calmodulin-mediated nuclear transport of the sex-determining region of the Y chromosome (SRY) in XY sex reversal.
abstract: The sex-determining region of the Y chromosome (SRY) plays a key role in human sex determination, as mutations in SRY can cause XY sex reversal. Although some SRY missense mutations affect DNA binding and bending activities, it is unclear how others contribute to disease. The high mobility group domain of SRY has two nuclear localization signals (NLS). Sex-reversing mutations in the NLSs affect nuclear import in some patients, associated with defective importin-beta binding to the C-terminal NLS (c-NLS), whereas in others, importin-beta recognition is normal, suggesting the existence of an importin-beta-independent nuclear import pathway. The SRY N-terminal NLS (n-NLS) binds calmodulin (CaM) in vitro, and here we show that this protein interaction is reduced in vivo by calmidazolium, a CaM antagonist. In calmidazolium-treated cells, the dramatic reduction in nuclear entry of SRY and an SRY-c-NLS mutant was not observed for two SRY-n-NLS mutants. Fluorescence spectroscopy studies reveal an unusual conformation of SRY.CaM complexes formed by the two n-NLS mutants. Thus, CaM may be involved directly in SRY nuclear import during gonadal development, and disruption of SRY.CaM recognition could underlie XY sex reversal. Given that the CaM-binding region of SRY is well-conserved among high mobility group box proteins, CaM-dependent nuclear import may underlie additional disease states.
authors.affiliation: Prince Henry's Institute of Medical Research, Level 4 Block E, Monash Medical Centre, 246 Clayton Road, Clayton, Victoria 3168, Australia.
authors.forename: Helena
authors.initials: H
authors.lastname: Sim
authors.forename: Kieran
authors.initials: K
authors.lastname: Rimmer
authors.forename: Sabine
authors.initials: S
authors.lastname: Kelly
authors.forename: Louisa M
authors.initials: LM
authors.lastname: Ludbrook
authors.forename: Andrew H A
authors.initials: AH
authors.lastname: Clayton
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Harley
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002147:Calmodulin / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D002522:Chlorocebus aethiops; D041321:Chromosomes, Human, X / Q000235:genetics; D041322:Chromosomes, Human, Y / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012734:Disorders of Sex Development; D005260:Female; D024282:Genes, sry / Q000235:genetics*; D024742:HMG-Box Domains / Q000235:genetics / Q000502:physiology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D004268:DNA-Binding Proteins; D007093:Imidazoles; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors; C031938:calmidazolium