FIG 8.

In type III latency, CTCF is PARylated by PARP1 at Cp to maintain the open chromatin landscape and transcription. (Top) During type III latency, PARP1 binds along with PARylated CTCF at the active Cp promoter. PARP1 and CTCF cooperate at Cp to promote open chromatin structure and active transcription by maintaining decondensed nucleosomes and H3K4me3 and preventing DNA methylation. (Bottom) PARP inhibition results in the loss of CTCF at Cp and is associated with the formation of a repressive chromatin environment at the Cp promoter. After PARP inhibition, the Cp promoter becomes enriched for DNA methylation, the repressive H3K27me3 mark, and the nucleosomes are compacted, resulting in decreased type III latency transcription.