The obligate intracellular bacterial pathogen Chlamydia trachomatis (Ctr) has been associated with cervical and ovarian cancer development. However, establishment of causality and the underlying mechanisms remain outstanding. Our analysis of Ctr-induced alterations to global host histone modifications revealed distinct patterns of histone marks during acute and persistent infections. In particular, pH2AX (Ser139) and H3K9me3, hallmarks of DNA double-strand breaks (DSBs) and senescence-associated heterochromatin foci (SAHF), respectively, showed sustained upregulation during Ctr infection. Ctr-induced reactive oxygen species were found to contribute to persistent DSBs, which in turn elicited SAHF formation in an ERK-dependent manner. Furthermore, Ctr interfered with DNA damage responses (DDR) by inhibiting recruitment of the DDR proteins pATM and 53BP1 to damaged sites. Despite impaired DDR, Ctr-infected cells continued to proliferate, supported by enhanced oncogenic signals involving ERK, CyclinE, and SAHF. Thus, by perturbing host chromatin, DSB repair, and cell-cycle regulation, Ctr generates an environment favorable for malignant transformation.

The transition zones of the squamous and columnar epithelia constitute hotspots for the emergence of cancer, often preceded by metaplasia, in which one epithelial type is replaced by another. It remains unclear how the epithelial spatial organization is maintained and how the transition zone niche is remodelled during metaplasia. Here we used single-cell RNA sequencing to characterize epithelial subpopulations and the underlying stromal compartment of endo- and ectocervix, encompassing the transition zone. Mouse lineage tracing, organoid culture and single-molecule RNA in situ hybridizations revealed that the two epithelia derive from separate cervix-resident lineage-specific stem cell populations regulated by opposing Wnt signals from the stroma. Using a mouse model of cervical metaplasia, we further show that the endocervical stroma undergoes remodelling and increases expression of the Wnt inhibitor Dickkopf-2 (DKK2), promoting the outgrowth of ectocervical stem cells. Our data indicate that homeostasis at the transition zone results from divergent stromal signals, driving the differential proliferation of resident epithelial lineages.

Mammalian cells possess sophisticated genome surveillance and repair mechanisms, executed by the so-called DNA damage response (DDR), failure of which leads to accumulation of DNA damage and genomic instability. Mounting evidence suggests that bacterial infections can elicit DNA damage in host cells, and certain pathogens induce such damage as part of their multi-faceted infection programme. Bacteria-mediated DNA damage can occur either directly through the formation of toxins with genotoxic activities or indirectly as a result of the activation of cell-autonomous or immune defence mechanisms against the pathogen. Moreover, host-cell signalling routes involved in the DDR can be altered in response to an infection, and this, in the context of DNA damage elicited by the pathogen, has the potential to trigger mutations and cancer.

Highlights d Phosphoproteome and transcriptome analyses reveal Ctrinduced host cell signaling d Ctr causes phosphorylation of MAPK/CDK and dephosphorylation of CAMK/PKA/PKC substrates d Ctr induces epithelial-to-mesenchymal transition via ERKmediated ERF and ETS1 signaling d Ctr-induced EMT conveys host cell invasiveness and disruption of cervical epithelium