title: Regulation of DNA polymerase beta by the LMP1 oncoprotein of EBV through the nuclear factor-kappaB pathway.
abstract: The repair DNA polymerase beta (Polbeta), when overexpressed, plays a critical role in generating genetic instability via its interference with the genomic replication program. Up-regulation of Polbeta has been reported in many tumor types that exhibit genetic aberrations, including EBV-related B-cell lymphomas. However, the mechanisms responsible for its overexpression have never been examined. Here, we report that both expression and activity of Polbeta, in EBV-immortalized B cells, are induced by several natural genetic variants of LMP1, an oncoprotein associated with the vast majority of EBV-related tumors. Conversely, we found that the expression of Polbeta decreased when LMP1 signaling was down-regulated by a dominant negative of LMP1 or an inhibitor of the nuclear factor-kappaB (NF-kappaB) pathway, the main transduction pathway activated by LMP1, strongly supporting a role of NF-kappaB in the LMP1-mediated Polbeta regulation. Using electrophoretic mobility shift assay experiments from several EBV-immortalized B-cell nuclear extracts, we identified an LMP1-dependent p50/c-Rel heterodimer on a proximal kappaB binding site (-211 to -199nt) of the Polbeta promoter. This result was correlated with a specific Polbeta kappaB transcriptional activity. Taken together, our data enlighten a new mechanism responsible for Polbeta overexpression in EBV-infected cells, mediated by LMP1 and dependent on NF-kappaB activation.
authors.affiliation: Institut National de la Sante et de la Recherche Medicale-U563, CPTP.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Faumont
authors.forename: Christophe
authors.initials: C
authors.lastname: Le Clorennec
authors.forename: Pierre
authors.initials: P
authors.lastname: Teira
authors.forename: Gauthier
authors.initials: G
authors.lastname: Goormachtigh
authors.forename: Jean
authors.initials: J
authors.lastname: Coll
authors.forename: Yvan
authors.initials: Y
authors.lastname: Canitrot
authors.forename: Christophe
authors.initials: C
authors.lastname: Cazaux
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Hoffmann
authors.forename: Pierre
authors.initials: P
authors.lastname: Brousset
authors.forename: Georges
authors.initials: G
authors.lastname: Delsol
authors.forename: Jean
authors.initials: J
authors.lastname: Feuillard
authors.forename: Fabienne
authors.initials: F
authors.lastname: Meggetto
mesh_terms: D000818:Animals; D001483:Base Sequence; D002461:Cell Line, Transformed; D004247:DNA; D019951:DNA Polymerase beta / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D014763:Viral Matrix Proteins / Q000502:physiology*
chemical_list: C037662:EBV-associated membrane antigen, Epstein-Barr virus; D016328:NF-kappa B; D014763:Viral Matrix Proteins; D004247:DNA; D019951:DNA Polymerase beta