Project Summary
Mycobacterium tuberculosis (Mtb) remains one of the most infectious and deadly pathogens worldwide. Key to
Mtb virulence are Mtb membrane-bound and secreted effector proteins that interact with host proteins to
influence the host response to infection and promote Mtb survival. Mtb has roughly 100 effector proteins, but few
of these effectors have been characterized or directly implicated in Mtb pathogenesis. There is emerging
evidence that many intracellular bacterial pathogens have evolved nuclear effector proteins (dubbed
nucleomodulins) that interfere with nuclear gene expression pathways like chromatin remodeling, histone
modification, transcription, and pre-mRNA splicing. The objectives of this proposal are two-fold: to define how
histone methylation changes at innate immune genes over the course of Mtb infection of macrophages, and to
investigate how a putative Mtb nucleomodulin evolved to manipulate host epigenetic control of gene expression.
Mtb secretes a protein called Rv1075c. Preliminary data demonstrates that Rv107c is upregulated early after
Mtb infection, ectopic expression of Rv1075c promotes hyperinduction of genes likes Ifnb1, and expression of
pro-bacterial inflammatory cytokines in dampened by a Rv1075c Mtb strain. Immunopurification of Rv1075c
enriches for multiple components of the mammalian SET1 histone methyltransferase complex (RBBP5, ASH2L,
WDR5), which deposits H3K4me3, a mark associated with transcriptional activation. This proposal is founded
on the hypothesis that Rv1075c interacts with the SET1 complex to alter histone methylation in Mtb-infected
macrophages to promote a specific pro-bacterial gene expression program. Aim 1 of this proposal will implicate
the SET1 histone methyltransferase complex in controlling innate immune gene expression in response to Mtb.
Aim 2 of this proposal will investigate how Rv1075c is secreted and how it traffics to the nucleus and how it
interacts with SET1 complex members. Aim 3 will investigate how Rv1075c expression controls macrophage
gene expression during Mtb infection. Through completion of these aims, this application will provide novel
insights into the role of Rv1075c in chromatin remodeling and broadly advance our understanding of bacterial
virulence mechanisms. It will also provide multiple training opportunities, including mastery of bacterial and
mammalian genetic approaches and the development of expertise working with an important human BSL3
pathogen.
