Palikyras, S. | Search bioRxiv

bioRxiv2024

Senescent cells cluster CTCF on nuclear speckles to sustain their splicing program

Senescence --the endpoint of replicative lifespan for normal cells-- is established via a complex sequence of molecular events. One such event is the dramatic reorganization of CTCF into senescence-induced clusters (SICCs). However, the molecular determinants, genomic consequences, and functional purpose of SICCs remained unknown. Here, we combine functional assays, super-resolution imaging, and 3D genomics with computational modelling to dissect SICC emergence. We establish that the competition between CTCF-bound and non-bound loci dictates clustering propensity. Upon senescence entry, cells repurpose SRRM2 --a key component of nuclear speckles-- and BANF1 --a molecular glue for chromosomes-- to cluster CTCF and rewire genome architecture. This CTCF-centric reorganization in reference to nuclear speckles functionally sustains the senescence splicing program, as SICC disruption fully reverts alternative splicing patterns. We therefore uncover a new paradigm, whereby cells translate changes in nuclear biochemistry into architectural changes directing splicing choices so as to commit to the fate of senescence. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/603680v1_ufig1.gif" ALT="Figure 1"> View larger version (85K): org.highwire.dtl.DTLVardef@cfb561org.highwire.dtl.DTLVardef@8cfdf3org.highwire.dtl.DTLVardef@7485d5org.highwire.dtl.DTLVardef@1fe9051_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIHMGB2-bound loci compete with CTCF-bound ones for nuclear speckle association C_LIO_LISenescent cells repurpose SRRM2 and BANF1 to cluster CTCF on speckles C_LIO_LIBANF1 is essential, but not sufficient for CTCF clustering C_LIO_LIThe SRRM2 RNA-binding domain directs CTCF clustering C_LIO_LISICCs rewire chromatin positioning to sustain the senescence splicing program C_LI

cell biology↗

bioRxiv2023

Rapid and synchronous chemical induction of replicative-like senescence via a small molecule inhibitor

Cellular senescence is now acknowledged as a key contributor to organismal ageing and late-life disease. Although popular, the study of senescence in vitro can be complicated by the prolonged and asynchronous timing of cells committing to it and its paracrine effects. To address these issues, we repurposed the small molecule inhibitor inflachromene (ICM) to induce senescence to human primary cells. Within six days of treatment with ICM, senescence hallmarks, including the nuclear eviction of HMGB1 and -B2, are uniformly induced across IMR90 cell populations. By generating and comparing various high throughput datasets from ICM-induced and replicative senescence, we uncovered significant similarity of the two states. Notably though, ICM suppresses the proinflammatory secretome associated with senescence, thus alleviating most paracrine effects. In summary, ICM induces a senescence-like phenotype rapidly and synchronously thereby allowing the study of its core regulatory program without any confounding heterogeneity.

genomics↗