CBFb Stabilizes HIV Vif to Counteract APOBEC3 at the Expense of RUNX1 Target Gene Expression [gene expression]
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ABSTRACT: 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. 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 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:Runx/Cbfb heterodimers play important roles in the development of hematopoietic cells in mouse embryos and adults. In order to identify genes that are regulated by Runx/Cbfb, we purified Lin– c-kit+ Sca1+ (LSK) cells and Lin– c-kit+ Sca1– CD16/32+ (GMP) cells from Vav1-iCre x Cbfb(F/F) and Vav1-iCre x Cbfb(F/+) mice and profiled gene expression using microarray.
Project description:Runx/Cbfb heterodimers play important roles in the development of hematopoietic cells in mouse embryos and adults. In order to identify genes that are regulated by Runx/Cbfb, we purified Lin– c-kit+ Sca1+ (LSK) cells and Lin– c-kit+ Sca1– CD16/32+ (GMP) cells from Vav1-iCre x Cbfb(F/F) and Vav1-iCre x Cbfb(F/+) mice and profiled gene expression using microarray. 200,000 LSK and GMP cells were purified separately from two 7 week old Vav1-iCre x Cbfb(F/F) mice and two Vav1-iCre x Cbfb(F/+) mice by cell sorting. The purity was higher than 98%. Total RNA was extracted using the NucleoSpin RNA XS kit (Macherey-Nagel), amplified using a PicoSL RNA amplification kit (Nugen) and biotinylated with Encore biotin module (Nugen). Labeled RNA was hybridized to Mouse Gene 1.0ST microarrays (Affymetrix) according to the manufacturer’s instruction.
Project description:Gene expression profiles of Cbfb-deficient and control Treg cells were compared. Abstract: Naturally arising regulatory T (Treg) cells express the transcription factor FoxP3, which critically controls the development and function of Treg cells. FoxP3 interacts with another transcription factor Runx1 (also known as AML1). Here we showed that Treg cell-specific deficiency of Cbfβ, a cofactor for all Runx proteins, or that of Runx1, but not Runx3, induced lymphoproliferation, autoimmune disease, and hyper-production of IgE. Cbfb-deleted Treg cells exhibited impaired suppressive function in vitro and in vivo, with altered gene expression profiles including attenuated expression of FoxP3 and high expression of interleukin-4. The Runx complex bound to more than 3000 gene loci in Treg cells, including the Foxp3 regulatory regions and the Il4 silencer. In addition, knockdown of RUNX1 showed that RUNX1 is required for the optimal regulation of FoxP3 expression in human T cells. Taken together, our results indicate that the Runx1-Cbfβ heterodimer is indispensable for in vivo Treg cell function, in particular, suppressive activity and optimal expression of FoxP3. Experiment Overall Design: CD4+CD25hi cells, most of which were Foxp3+ Treg cells, were isolated from Cbfb-flox/flox: Foxp3-ires-Cre (n = 3) and control Cbfb-flox/wt: Foxp3-ires-Cre (n = 3) mice. Total RNA was extracted from those purified Cbfb-deficient or control Treg cells.
Project description:Gene expression profiles of Cbfb-deficient and control Treg cells were compared. Abstract: Naturally arising regulatory T (Treg) cells express the transcription factor FoxP3, which critically controls the development and function of Treg cells. FoxP3 interacts with another transcription factor Runx1 (also known as AML1). Here we showed that Treg cell-specific deficiency of Cbfβ, a cofactor for all Runx proteins, or that of Runx1, but not Runx3, induced lymphoproliferation, autoimmune disease, and hyper-production of IgE. Cbfb-deleted Treg cells exhibited impaired suppressive function in vitro and in vivo, with altered gene expression profiles including attenuated expression of FoxP3 and high expression of interleukin-4. The Runx complex bound to more than 3000 gene loci in Treg cells, including the Foxp3 regulatory regions and the Il4 silencer. In addition, knockdown of RUNX1 showed that RUNX1 is required for the optimal regulation of FoxP3 expression in human T cells. Taken together, our results indicate that the Runx1-Cbfβ heterodimer is indispensable for in vivo Treg cell function, in particular, suppressive activity and optimal expression of FoxP3.
Project description:It is known that CBFB-MYH11, the fusion gene generated by inversion of chromosome 16 in human acute myeloid leukemia, is causative for oncogenic transformation. However, the mechanism by which CBFB-MYH11 initiates leukemogenesis is not clear. Previously published reports showed that CBFB-MYH11 dominantly inhibits RUNX1 and CBFB, and such inhibition has been suggested as the mechanism for leukemogenesis. However, knockin mice expressing Cbfb-MYH11 (Cbfb+/MYH11) showed defects in primitive hematopoiesis not seen in Cbfb null (Cbfb-/-) embryos indicating that Cbfb-MYH11 has repression independent activities as well. To identify gene expression changes associated with this novel activity, we compared the gene expression profile in the blood cells of Cbfb+/MYH11 and Cbfb-/- embryonic day 12.5 (E12.5) embryos with that of their wildtype littermates. Cbfb-MYH11 chimeras were mated to C57/Bl6 females to generate Cbfb+/MYH11 (Cbfb+/MYH11) and Cbfb+/+ (WT) embryos. Cbfb+/- x Cbfb+/- matings were used to generate Cbfb+/+ (Cbfb+/+) and Cbfb-/- (Cbfb-/-) embryos. Blood from 8-10 E12.5 embryos of the same genotype was pooled, and RNA was isolated, labeled, and hybridized to Affymetrix Genechip mouse microarray (430 2.0) chips. 4 chips were used for both the Cbfb+/MYH11 and littermate control samples. 3 chips were used for the Cbfb-/- samples and littermate control samples.
Project description:It is known that CBFB-MYH11, the fusion gene generated by inversion of chromosome 16 in human acute myeloid leukemia, is causative for oncogenic transformation. However, the mechanism by which CBFB-MYH11 initiates leukemogenesis is not clear. Previously published reports showed that CBFB-MYH11 dominantly inhibits RUNX1 and CBFB, and such inhibition has been suggested as the mechanism for leukemogenesis. However, knockin mice expressing Cbfb-MYH11 (Cbfb+/MYH11) showed defects in primitive hematopoiesis not seen in Cbfb null (Cbfb-/-) embryos indicating that Cbfb-MYH11 has repression independent activities as well. To identify gene expression changes associated with this novel activity, we compared the gene expression profile in the blood cells of Cbfb+/MYH11 and Cbfb-/- embryonic day 12.5 (E12.5) embryos with that of their wildtype littermates.