PROJECT SUMMARY
Innate immune sensing of microbes leads to activation of signal transduction cascades that trigger
multiple transcription factors to rewire gene expression for host defense. However, the mechanisms that regulate
this sophisticated response are not completely understood. This proposal addresses a novel transcriptional
mechanism that regulates the innate response to HIV-1. Our preliminary data define a gene regulatory network
that maps the innate immune response in monocyte-derived dendritic cells, and highlight new transcriptional
circuitry that controls interferon signaling, which is highly relevant for HIV infection. Type I and type III interferon
are known to block acute infection of HIV. However, dysregulated interferon signaling is a hallmark of
pathogenesis and can increase virus replication and spread. Based on our network predictions and experimental
validations, our data indicate that Core-Binding Factor Subunit Beta (CBFb, encoded by the gene CBFB) is a
cell-type specific regulator of interferon and inflammation. Loss-of-function mutations in CBFb have been
associated with breast cancer and acute myeloid leukemia, but a role in regulating antiviral responses through
interferon signaling has not been described. We have found that perturbation of CBFb by CRISPR-Cas9 or RNA
interference leads to spontaneous induction of specific interferon stimulated genes and inflammatory factors in
myeloid cells but not T cells. CBFb is known to be hijacked by HIV-1 Vif in T cells to reduce expression of
APOBEC3 family restriction factors, and our work suggests that CBFb’s impact on HIV is more complex than
previously appreciated. Interestingly, our data indicate that HIV-1 replicates more efficiently in CBFb-depleted
myeloid cells in single-cycle infections, but the virus fails to spread efficiently in replication-competent assays
(and in this case, effects are independent of Vif). The experiments outlined in this proposal will provide a greater
mechanistic understanding of how the transcription cofactor CBFb regulates innate immune responses and
influences HIV-1 replication. With this project we aim to: 1) Determine the direct and indirect targets of CBFb
and their impact on HIV infection, 2) Determine the mechanism by which CBFb limits IFN responses in myeloid
cells, and 3) Validate roles for CBFb during activation and maturation of primary immune cells in response to
HIV. We will systematically test how CBFb and CBFb-dependent genes impact HIV replication, test mutant CBFb
constructs in rescue experiments, and evaluate the roles of CBFb binding partners (such as RUNX family
members) in regulating HIV infection and the innate immune response. We expect to uncover the molecular
mechanism of how CBFb suppresses interferon signaling and gain a better understanding of how the
inflammatory state of a cell affects HIV replication. Ultimately, this project will teach us how cellular parameters
tune innate immunity, knowledge that could lead to new treatments to target the virus reservoir and engage anti-
HIV immune responses.