title: Deletion of Kaposi's sarcoma-associated herpesvirus FLICE inhibitory protein, vFLIP, from the viral genome compromises the activation of STAT1-responsive cellular genes and spindle cell formation in endothelial cells.
abstract: Kaposi's sarcoma herpesvirus (KSHV) Fas-associated death domain (FADD)-like interleukin-1 beta-converting enzyme (FLICE)-inhibitory protein, vFLIP, has antiapoptotic properties, is a potent activator of the NF-κB pathway, and induces the formation of endothelial spindle cells, the hallmark of Kaposi's sarcoma, when overexpressed in primary endothelial cells. We used a reverse genetics approach to study several functions of KSHV vFLIP in the context of the whole viral genome. Deletion of the gene encoding vFLIP from a KSHV genome cloned in a bacterial artificial chromosome (BAC) reduced the ability of the virus to persist and induce spindle cell formation in primary human umbilical vein endothelial cells (HUVECs). Only a few, mainly interferon (IFN)-responsive, genes were expressed in wild-type KSHV (KSHV-wt)-infected endothelial cells at levels higher than those in KSHV-ΔFLIP-infected endothelial cells, in contrast to the plethora of cellular genes induced by overexpressed vFLIP. In keeping with this observation, vFLIP induces the phosphorylation of STAT1 and STAT2 in an NF-κB-dependent manner in endothelial cells. vFLIP-dependent phosphorylation of STAT1 and STAT2 could be demonstrated after endothelial cells were infected with KSHV-wt, KSHV-ΔFLIP, and a KSHV-vFLIP revertant virus. These findings document the impact of KSHV vFLIP on the transcriptome of primary endothelial cells during viral persistence and highlight the role of vFLIP in the activation of STAT1/STAT2 and STAT-responsive cellular genes by KSHV.
authors.affiliation: Institut für Virologie, Hannover Medical School, Hannover, Germany.
authors.forename: Khaled R
authors.initials: KR
authors.lastname: Alkharsah
authors.forename: Vivek Vikram
authors.initials: VV
authors.lastname: Singh
authors.forename: Raffaella
authors.initials: R
authors.lastname: Bosco
authors.forename: Susann
authors.initials: S
authors.lastname: Santag
authors.forename: Adam
authors.initials: A
authors.lastname: Grundhoff
authors.forename: Andreas
authors.initials: A
authors.lastname: Konrad
authors.forename: Michael
authors.initials: M
authors.lastname: Stürzl
authors.forename: Dagmar
authors.initials: D
authors.lastname: Wirth
authors.forename: Oliver
authors.initials: O
authors.lastname: Dittrich-Breiholz
authors.forename: Michael
authors.initials: M
authors.lastname: Kracht
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Schulz
mesh_terms: D002478:Cells, Cultured; D042783:Endothelial Cells / Q000821:virology*; D017353:Gene Deletion; D019288:Herpesvirus 8, Human / Q000472:pathogenicity*; D054884:Host-Pathogen Interactions; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D050795:STAT2 Transcription Factor / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D016328:NF-kappa B; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D014764:Viral Proteins; D037521:Virulence Factors; C481275:viral FLIP protein, Human herpesvirus 8