GSE49341
Redistribution of the Lamin B1 genomic binding profile affects spatial rearrangement of heterochromatic domains and gene expression during senescence
Senescence is a stress responsive form of stable cell cycle exit. Senescent cells have a distinct gene expression profile, which is often accompanied by the spatial redistribution of heterochromatin into senescence-associated heterochromatic foci (SAHFs). Studying a key component of the nuclear lamina, lamin B1 (LMNB1), we report dynamic alterations in its genomic profile and their implications for SAHF formation and gene regulation during senescence. Genome-wide mapping reveals that LMNB1 is depleted during senescence, preferentially from the central regions of lamina-associated domains (LADs), which are enriched for H3K9me3. LMNB1 knockdown facilitates the spatial relocalization of perinuclear H3K9me3, thus promoting SAHF formation, which is inhibited by ectopic LMNB1 expression. Furthermore, despite the global reduction in LMNB1 protein levels, LMNB1 binding increases during senescence in a small subset of gene-rich regions where H3K27me3 also increases and gene expression becomes repressed. These results suggest that LMNB1 may contribute to senescence in at least two ways due to its uneven genomewide redistribution: firstly through the spatial re-organization of chromatin and, secondly, through gene repression. Overall design: ChIP-seq for Lamin B1 in Growing and Ras Induced Senescence