Cis-regulatory effect of HPV integration is constrained by host chromatin architecture in cervical cancers

Human papillomavirus (HPV) infections are the primary drivers of cervical cancers, and often HPV DNA gets integrated into the host genome. Although the oncogenic impact of HPV encoded genes is relatively well known, the cis-regulatory effect of integrated HPV DNA on host chromatin structure and gene regulation remains less understood. We investigated genome-wide patterns of HPV integrations and associated host gene expression changes in the context of host chromatin states and topologically associating domains (TADs). HPV integrations were significantly enriched in active chromatin regions and depleted in inactive ones. Interestingly, regardless of chromatin state, genomic regions flanking HPV integrations showed transcriptional upregulation. Nevertheless, upregulation (both local and long-range) was mostly confined to TADs with integration, but not affecting adjacent TADs. Few TADs showed recurrent integrations associated with overexpression of oncogenes within them (e.g. MYC, PVT1, TP63 and ERBB2) regardless of proximity. Hi-C and 4C-seq analyses in cervical cancer cell line (HeLa) demonstrated chromatin looping interactions between integrated HPV and MYC/PVT1 regions (similar to 500 kb apart), leading to allele-specific overexpression. Based on these, we propose HPV integrations can trigger multimodal oncogenic activation to promote cancer progression.

Automated summary

The integration of human papillomavirus (HPV) into the host genome affects the expression of adjacent genes, and this study reveals that the effects differ depending on the chromatin state at the integration site. The integration of HPV leads to the upregulation of nearby genes within the same topologically associating domains (TADs), but does not affect genes in adjacent TADs. Recurrent HPV integration in specific TADs results in the overexpression of oncogenes.