Abstract
Although cellular senescence is accompanied by global alterations in genome architecture, how the genome is restructured during the senescent processes is not well understood. Here, we show that the hCAP-H2 subunit of the condensin II complex exists as either a full-length protein or an N-terminus truncated variant (ΔN). While the full-length hCAP-H2 associates with mitotic chromosomes, the ΔN variant exists as an insoluble nuclear structure. When overexpressed, both hCAP-H2 isoforms assemble this nuclear architecture and induce senescence-associated heterochromatic foci (SAHF). The hCAP-H2ΔN protein accumulates as cells approach senescence, and hCAP-H2 knockdown inhibits oncogene-induced senescence. This study identifies a novel mechanism whereby condensin drives senescence via nuclear/genomic reorganization.
Keywords:
BrdU, bromodeoxyuridine; CDK, cyclin dependent kinase; DAPI, 4,6-diamidino-2-phenylindole; NCAPH2, non-SMC chromosome-associated protein H2 gene; RPE-1, hTERT-immortalized retinal pigment epithelial cell line; Rb, retinoblastoma protein; SA-β-gal, senescence-associated β-galactosidase; SADS, senescence-associated distension of satellites; SAHF; SAHF, senescence-associated heterochromatic foci; SMC, structural maintenance of chromosomes; cellular senescence; condensin; genome organization; hCAP-H2, human chromosome-associated protein H2; hTERT, human telomerase reverse transcriptase; human; nuclear architecture; oncogene-induced senescence; shRNA, short-hairpin RNA.; uORF, upstream open reading frame.