title: Expression of the GTP-binding protein Gαs in human myometrial cells is regulated by ubiquitination and protein degradation: involvement of proteasomal inhibition by trichostatin A.
abstract: In this study, we show that myometrial transcriptional complexes consisting of Sp1, Sp3, histone deacetylase (HDAC)1/2, RbAp48, and mSin3A are recruited to 4 out of the 6 Sp1-4 sites within the Gαs promoter. Moreover disruption in the binding of these complexes via mithramycin administration results in a substantial decrease in expression of Gαs proteins in myometrial cell cultures. In many instances, these transcriptional regulatory complexes repress expression of genes having a high CG content within their promoter region. This repression can be attenuated by inhibition of HDAC activity by the class I/II HDAC inhibitor trichostatin A (TSA) resulting in increased gene transcription. However, although a substantial increase in Gαs protein levels was observed upon administration of TSA to primary cultures of human myometrial cells, this was not preceded by an increase in messenger RNA (mRNA) and thus an elevation in gene transcription. Importantly the increase in Gαs protein levels occurred via ubiquitination and inhibition of proteasomal activity, indicating that this pathway is also involved in regulating Gαs protein expression during pregnancy and parturition.
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Faculty of Medical Sciences, Newcastle upon Tyne, England, UK. magda.karolczak@nil.ac.uk
authors.forename: Magdalena
authors.initials: M
authors.lastname: Karolczak-Bayatti
authors.forename: Tamer M M
authors.initials: TM
authors.lastname: Abu-Amara
authors.forename: G Nicholas
authors.initials: GN
authors.lastname: Europe-Finner
mesh_terms: D002478:Cells, Cultured; D005260:Female; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006655:Histone Deacetylases; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D009215:Myometrium / Q000378:metabolism*; D011247:Pregnancy; D011401:Promoter Regions, Genetic / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects; D059748:Proteolysis; D012333:RNA, Messenger / Q000032:analysis; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D044385:GTP-Binding Protein alpha Subunits; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D012333:RNA, Messenger; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; C012589:trichostatin A; D046988:Proteasome Endopeptidase Complex; D006655:Histone Deacetylases