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Loss of lamin B1 results in prolongation of S-phase and decondensation of chromosome territories in the interphase nucleus of mammalian cells

ABSTRACT: Nuclear lamin B1 constitutes one of the major structural proteins in the lamina mesh. We silenced the expression of lamin B1 by RNA interference in the colon cancer cell line DLD-1 and showed a dramatic redistribution of H3K27me3 from the periphery to a more homogeneous nuclear dispersion; in addition we observed an increased frequency of micronuclei and nuclear blebs. By 3D-FISH analyses, we demonstrate that the volume and surface of chromosome territories were significantly larger in LMNB1-depleted cells, suggesting that lamin B1 is required to maintain chromatin condensation in interphase nuclei. These changes led to a prolonged S-phase due to activation of Chk1 and telomere attrition. Finally, silencing of LMNB1 resulted in extensive changes in alternative splicing of multiple genes and in a higher number of enlarged nuclear speckles. Taken together, our results suggest a mechanistic role of the nuclear lamina in the organization of chromosome territories, maintenance of genome integrity and proper gene splicing. This dataset includes the comparison of gene transcripts between cells with silenced lamin B1 and empty vector negative control transfected cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE53546 | GEO | 2014/07/16

SECONDARY ACCESSION(S): PRJNA232371

REPOSITORIES: GEO

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Project description:Purpose: Many mammalian genes exhibit circadian expression patterns concordant with periodic binding of transcription factors, chromatin modifications and chromosomal interactions. We determined whether lamina-associated domains (LADs) display oscillatory circadian patterns of interaction with nuclear lamin B1 during hte circadian cycle, and identified any relationship to changes in gene expression patterns in oscillatory LADs or in their vinicity. Methods: To this end, we mapped LADs by chromatin immunoprecipitation-sequencing (ChIP-seq) of lamin B1 (LMNB1) (antibody ab16048, Abcam) from mouse livers colected every 6 h, for 30 h, after entrainment of the circadian clock by 24-h fasting and refeeding. Gene expression profiles were also analyzed by RNA-sequencing (RNA-seq) at the same time points. Results and Conclusions: We report periodic interactions of chromatin domains with nuclear lamin B1, suggesting rhythmic associations of fractions of the genome with the nuclear lamina. Entrainment of the circadian clock by fasting and refeeding is accompanied in mouse liver by a gain of lamin-chromatin interactions followed by oscillations in these interactions at hundreds of lamina-associated domains (LADs). A subset of these oscillations exhibit periodicity and affect one or both LAD borders or entire stand-alone LADs. Periodic LADs are however not a dominant feature of these variable LADs, as most LADs are conserved during the circadian cycle. LAD oscillations are for the most part asynchronous between the 5’ and 3’ ends of LADs. Periodic LADs also uncoupled from gene expression patterns, periodic or not, within or in vicinity of these LADs. Accordingly, periodic genes, including central clock-control genes, are located megabases away from LADs, suggesting their residence in a transcriptionally permissive environment throughout the circadian cycle. Our data suggest autonomous oscillatory associations of fractions of the genome with the nuclear lamina, providing new evidence for rhythmic spatial configurations of chromatin. However, our data also argue that periodic LADs constitute a minor fraction of variable LADs, and reflect stochasticity in variable lamin-chromatin interactions during the circadian cycle.

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Loss of lamin B1 results in prolongation of S-phase and decondensation of chromosome territories in the interphase nucleus of mammalian cells

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