Genome-wide mapping of H4K20me3 in proliferating and senescent IMR90 cells.

Cellular senescence is a stable proliferation arrest and tumor suppressor mechanism. Abundance of histone modification, H4K20me3, has been reported to increase in senescent cells. Generally, H4K20me3 promotes formation of compacted transcriptionally silent constitutive heterochromatin, but its specific role in senescence is unknown. Here, we show that in senescent cells H4K20me3 is enriched at specific families of gene repeats (ZNFs, Olfactory Receptors, Protocadherins), and DNA sequences contained within senescence-associated heterochromatin (senescence-associated heterochromatin (SAHF)). Furthermore, in senescent cells, but not proliferating cells, H4K20me3 is also markedly enriched at bodies of repressed genes, including proliferation-promoting genes. Ectopic expression of SUV420H2, responsible for deposition of H4K20me3, reinforces senescence-associated proliferation arrest, and slows proliferation of transformed cells and tumorigenesis in vivo. These results indicate a dedicated role for H4K20me3 in control of nuclear organization and gene expression in senescent cells and stable senescence-associated proliferation arrest and tumor suppression.