The 20S proteasome activator PA28? controls the compaction of chromatin

ABSTRACT PA28? (also known as PSME3), a nuclear activator of the 20S proteasome, is involved in degradation several proteins regulating cell growth and proliferation dynamics various bodies, but its precise cellular functions remain unclear. Here, using quantitative FLIM-FRET based microscopy assay monitoring close proximity between nucleosomes living human cells, we show that controls chromatin compaction. We find depletion induces decompaction pericentromeric heterochromatin, which similar to what observed upon knockdown HP1? CBX1), key factor heterochromatin structure. present at HP1?-containing repetitive DNA sequences abundant and, importantly, on own unable drive compaction without presence PA28?. At molecular level, this novel function independent stable interaction with most likely depends ability maintain appropriate levels H3K9me3 H4K20me3, histone modifications are formation. Overall, our results implicate regulation higher order structure chromatin.