Project description:The HIV-1 accessory protein Vif hijacks a cellular Cullin-RING ubiquitin ligase, CRL5, to promote degradation of the APOBEC3 (A3) family of restriction factors. Recently, the cellular transcription cofactor CBFb was shown to form a complex with CRL5-Vif and to be essential for A3 degradation and viral infectivity. We now demonstrate that CBFb is required for assembling a well-ordered CRL5-Vif complex by inhibiting Vif oligomerization and by activating CRL5-Vif via direct interaction. The CRL5-Vif-CBFb holoenzyme forms a welldefined heterohexamer, indicating that Vif simultaneously hijacks CRL5 and CBFb. Heterodimers of CBFb and RUNX transcription factors contribute toward the regulation of genes, including those with immune system functions. We show that binding of Vif to CBFb is mutually exclusive with RUNX heterodimerization and impacts the expression of genes whose regulatory domains are associated with RUNX1. Our results provide a mechanism by which a pathogen with limited coding capacity uses one factor to hijack multiple host pathways. Identification of RUNX1 binding sites in the Jurkat cell line
Project description:The HIV-1 accessory protein Vif hijacks a cellular Cullin-RING ubiquitin ligase, CRL5, to promote degradation of the APOBEC3 (A3) family of restriction factors. Recently, the cellular transcription cofactor CBFb was shown to form a complex with CRL5-Vif and to be essential for A3 degradation and viral infectivity. We now demonstrate that CBFb is required for assembling a well-ordered CRL5-Vif complex by inhibiting Vif oligomerization and by activating CRL5-Vif via direct interaction. The CRL5-Vif-CBFb holoenzyme forms a wellde?ned heterohexamer, indicating that Vif simultaneously hijacks CRL5 and CBFb. Heterodimers of CBFb and RUNX transcription factors contribute toward the regulation of genes, including those with immune system functions. We show that binding of Vif to CBFb is mutually exclusive with RUNX heterodimerization and impacts the expression of genes whose regulatory domains are associated with RUNX1. Our results provide a mechanism by which a pathogen with limited coding capacity uses one factor to hijack multiple host pathways. Analysis of Vif-dependent effects on gene expression in Jurkats when cells are activated for 4 or 6 hours with PMA and PHA
Project description:The HIV-1 accessory protein Vif hijacks a cellular Cullin-RING ubiquitin ligase, CRL5, to promote degradation of the APOBEC3 (A3) family of restriction factors. Recently, the cellular transcription cofactor CBFb was shown to form a complex with CRL5-Vif and to be essential for A3 degradation and viral infectivity. We now demonstrate that CBFb is required for assembling a well-ordered CRL5-Vif complex by inhibiting Vif oligomerization and by activating CRL5-Vif via direct interaction. The CRL5-Vif-CBFb holoenzyme forms a welldefined heterohexamer, indicating that Vif simultaneously hijacks CRL5 and CBFb. Heterodimers of CBFb and RUNX transcription factors contribute toward the regulation of genes, including those with immune system functions. We show that binding of Vif to CBFb is mutually exclusive with RUNX heterodimerization and impacts the expression of genes whose regulatory domains are associated with RUNX1. Our results provide a mechanism by which a pathogen with limited coding capacity uses one factor to hijack multiple host pathways.
Project description:The HIV-1 accessory protein Vif hijacks a cellular Cullin-RING ubiquitin ligase, CRL5, to promote degradation of the APOBEC3 (A3) family of restriction factors. Recently, the cellular transcription cofactor CBFb was shown to form a complex with CRL5-Vif and to be essential for A3 degradation and viral infectivity. We now demonstrate that CBFb is required for assembling a well-ordered CRL5-Vif complex by inhibiting Vif oligomerization and by activating CRL5-Vif via direct interaction. The CRL5-Vif-CBFb holoenzyme forms a welldefined heterohexamer, indicating that Vif simultaneously hijacks CRL5 and CBFb. Heterodimers of CBFb and RUNX transcription factors contribute toward the regulation of genes, including those with immune system functions. We show that binding of Vif to CBFb is mutually exclusive with RUNX heterodimerization and impacts the expression of genes whose regulatory domains are associated with RUNX1. Our results provide a mechanism by which a pathogen with limited coding capacity uses one factor to hijack multiple host pathways.
Project description:The seminal description of cellular restriction factor APOBEC3G and its antagonism by HIV-1 Vif has underpinned two decades of research on the host-virus interaction. As well as APOBEC3G and its homologues, however, we have recently discovered that Vif is also able to degrade the PPP2R5 family of regulatory subunits of key cellular phosphatase PP2A (PPP2R5A-E) (Greenwood et al., 2016; Naamati et al., 2019). We now identify amino acid polymorphisms at positions 31 and 128 of HIV-1 Vif which selectively regulate the degradation of PPP2R5 family proteins. These residues covary across HIV-1 viruses in vivo, favouring depletion of PPP2R5A-E. Through analysis of point mutants and naturally occurring Vif variants, we further show that degradation of PPP2R5 family subunits is both necessary and sufficient for Vif-dependent G2/M cell cycle arrest. Antagonism of PP2A by HIV-1 Vif is therefore independent of APOBEC3 family proteins, and regulates cell cycle progression in HIV-infected cells.
Project description:APOBEC3G and APOBEC3F are cell-encoded restriction factors that have evolved to counteract virus infections. When packaged into HIV-1 particles, A3G and A3F impair reverse transcription and induce the hypermutation of viral DNA. We employed a next generation sequencing approach to identify the RNAs that these proteins bind in HIV-1 infected cells and HIV-1 virions. We then analysed the mechanism of packaging of APOBEC3 in detail.
Project description:To identify the target genes of Runx1/Cbfb in MLL fusion leukemia, we performed microarray analysis using control and Runx1/Cbfb-deleted MLL-AF9 cells.
Project description:We searched for genes which are mutated in a manner that is linked with gene mutations involved in DNA de/methylation in AML. We found that recurrent CBFB-MYH11 fusions, which result in the expression of fusion protein comprising core-binding factor β (CBFB) and myosin heavy chain 11 (MYH11), occur mutually exclusively with DNMT3A mutations. The CBFB-MYH11 fusion tumors show DNA hypomethylation patterns similar to cancers with loss-of-function mutation of DNMT3A. Expression of CBFB-MYH11 fusion protein or inhibition of DNMT3A similarly impairs the methylation and expression of target genes of Runt related transcription factor 1 (RUNX1), a functional partner of CBFB. We demonstrate that RUNX1 directly interacts with DNMT3A and that CBFB-MYH11 fusion protein sequesters RUNX1 in the cytoplasm, thereby preventing RUNX1 from interacting with and recruiting DNMT3A to its target genes. Our results identify a novel regulation of DNA methylation and provide a molecular basis how CBFB-MYH11 fusion contributes to leukemogenesis.