Epigenetic landscape of the H3K27me3 mark in macrophages transformed by Theileria annulata infection

Theileria annulata infection transforms bovine leukocytes that display similarities to human leukomas. Post-translational modifications of histone tails control chromatin structure and epigenetically orchestrate gene expression. We deciphered the epigenetic landscape of T. annulata-transformed macrophages and compared the landscapes between virulent highly disseminating macrophages versus attenuated macrophages with diminished dissemination. Western blot and ChIP-seq showed a higher global level of H3K27me3 and unusual distribution of H3K27me3 marks in attenuated macrophages. Expression of many genes marked by H3K27me3 didn't regain transcription following PRC2 inhibitor treatment that removed H3K27me3 marks. This indicates that altered H3K27me3 marks had lost their classical silencing function and spreading of H3K27me3 marks might have a novel function unrelated to maintaining genes in a transcriptionally silenced state.