The Mycobacterium tuberculosis secreted protein Rv1075c hijacks host histone methyltransferases to promote infection - 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.
