Overexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activity

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dc.contributor.authorvan der Watt, Pauline Jen_ZA
dc.contributor.authorNgarande, Ellenen_ZA
dc.contributor.authorLeaner, Virna Den_ZA
dc.date.accessioned2016-01-02T05:07:43Z
dc.date.available2016-01-02T05:07:43Z
dc.date.issued2011en_ZA
dc.description.abstractThe Karyopherin superfamily comprises nuclear transport proteins, involved in the shuttling of certain cargo proteins into and out of the nucleus. Karyopherin β1 (Kpnβ1) and Karyopherin α2 (Kpnα2) are importin proteins, which work in concert to transport their cargo into the nucleus. We previously identified increased expression of Kpnβ1 and Kpnα2 in cervical tumours compared to normal epithelium and in transformed cells compared to their normal counterparts. This study therefore aimed to identify the transcription regulatory mechanisms associated with high Kpnβ1 and Kpnα2 levels in cancer cells. Kpnβ1 (−2013 to +100) and Kpnα2 (−1900 to +69) promoter fragments were separately cloned into the reporter vector, pGL3-basic, and luciferase assays revealed both as significantly more active in cancer and transformed cells compared to normal. A series of deletion constructs identified the −637 to −271 Kpnβ1 and −180 to −24 Kpnα2 promoter regions as responsible for the differential promoter activity, and a number of highly conserved E2F binding sites were identified within these regions. Mutation analysis confirmed the requirement of E2F sites for promoter activity, and ChIP analysis confirmed E2F2/Dp1 binding to the Kpnβ1 and Kpnα2 promoters in vivo . Dp1 inhibition resulted in decreased levels of the respective proteins, confirming the role of E2F in the overexpression of Kpnβ1 and Kpnα2 proteins in cancer. E2F activity is known to be deregulated in cervical cancer cells due to the inhibition of its repressor, Rb, by HPV E7. The inhibition of E7 using siRNA resulted in decreased Kpnβ1 and Kpnα2 promoter activities, as did the overexpression of Rb. In conclusion, this study is a first to show that elevated Kpnβ1 and Kpnα2 expression in cancer cells correlates with altered transcriptional regulation associated with deregulated E2F/Rb activities.en_ZA
dc.identifier.apacitationvan der Watt, P. J., Ngarande, E., & Leaner, V. D. (2011). Overexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activity. <i>PLoS One</i>, http://hdl.handle.net/11427/16178en_ZA
dc.identifier.chicagocitationvan der Watt, Pauline J, Ellen Ngarande, and Virna D Leaner "Overexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activity." <i>PLoS One</i> (2011) http://hdl.handle.net/11427/16178en_ZA
dc.identifier.citationVan Der Watt, P. J., Ngarande, E., & Leaner, V. D. (2011). Overexpression of Kpnb1 and Kpna2 Importin Proteins in Cancer Derives from Deregulated E2F Activity, PLoS ONE, 6(11), e27723. doi:10.1371/journal.pone.0027723en_ZA
dc.identifier.ris TY - Journal Article AU - van der Watt, Pauline J AU - Ngarande, Ellen AU - Leaner, Virna D AB - The Karyopherin superfamily comprises nuclear transport proteins, involved in the shuttling of certain cargo proteins into and out of the nucleus. Karyopherin β1 (Kpnβ1) and Karyopherin α2 (Kpnα2) are importin proteins, which work in concert to transport their cargo into the nucleus. We previously identified increased expression of Kpnβ1 and Kpnα2 in cervical tumours compared to normal epithelium and in transformed cells compared to their normal counterparts. This study therefore aimed to identify the transcription regulatory mechanisms associated with high Kpnβ1 and Kpnα2 levels in cancer cells. Kpnβ1 (−2013 to +100) and Kpnα2 (−1900 to +69) promoter fragments were separately cloned into the reporter vector, pGL3-basic, and luciferase assays revealed both as significantly more active in cancer and transformed cells compared to normal. A series of deletion constructs identified the −637 to −271 Kpnβ1 and −180 to −24 Kpnα2 promoter regions as responsible for the differential promoter activity, and a number of highly conserved E2F binding sites were identified within these regions. Mutation analysis confirmed the requirement of E2F sites for promoter activity, and ChIP analysis confirmed E2F2/Dp1 binding to the Kpnβ1 and Kpnα2 promoters in vivo . Dp1 inhibition resulted in decreased levels of the respective proteins, confirming the role of E2F in the overexpression of Kpnβ1 and Kpnα2 proteins in cancer. E2F activity is known to be deregulated in cervical cancer cells due to the inhibition of its repressor, Rb, by HPV E7. The inhibition of E7 using siRNA resulted in decreased Kpnβ1 and Kpnα2 promoter activities, as did the overexpression of Rb. In conclusion, this study is a first to show that elevated Kpnβ1 and Kpnα2 expression in cancer cells correlates with altered transcriptional regulation associated with deregulated E2F/Rb activities. DA - 2011 DB - OpenUCT DO - 10.1371/journal.pone.0027723 DP - University of Cape Town J1 - PLoS One LK - https://open.uct.ac.za PB - University of Cape Town PY - 2011 T1 - Overexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activity TI - Overexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activity UR - http://hdl.handle.net/11427/16178 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/16178
dc.identifier.urihttp://dx.doi.org/10.1371/journal.pone.0027723
dc.identifier.vancouvercitationvan der Watt PJ, Ngarande E, Leaner VD. Overexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activity. PLoS One. 2011; http://hdl.handle.net/11427/16178.en_ZA
dc.language.isoengen_ZA
dc.publisherPublic Library of Scienceen_ZA
dc.publisher.departmentDivision of Medical Biochemistryen_ZA
dc.publisher.facultyFaculty of Health Sciencesen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.rightsThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.en_ZA
dc.rights.holder© 2011 van der Watt et alen_ZA
dc.rights.urihttp://creativecommons.org/licenses/by/4.0en_ZA
dc.sourcePLoS Oneen_ZA
dc.source.urihttp://journals.plos.org/plosoneen_ZA
dc.subject.otherCervical canceren_ZA
dc.subject.otherSmall interfering RNAsen_ZA
dc.subject.otherGene regulationen_ZA
dc.subject.otherLuciferaseen_ZA
dc.subject.otherGene expressionen_ZA
dc.subject.otherPolymerase chain reactionen_ZA
dc.subject.otherCargo proteinsen_ZA
dc.subject.otherTransfectionen_ZA
dc.titleOverexpression of Kpnβ1 and Kpnα2 Importin Proteins in Cancer Derives from Deregulated E2F Activityen_ZA
dc.typeJournal Articleen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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