Project description:We developed a new sequencing assay to track the de novo deposition of the histone H3 variants H3.1 and H3.3 during S phase. We use cells stably expressing H3.1-SNAP or H3.3-SNAP, and synchronize them in G1/S by double-thymidine block. The SNAP-tag enables to discriminate newly synthesized histones from preexisting ones, via a quench-chase-capture strategy. We applied this strategy to isolate new H3.1 and H3.3 after releasing cells into S phase, and probed their distribution by MNase digestion and sequencing. We could thus characterize H3.1 and H3.3 dynamics from early to mid S phase at genome-wide resolution. We further applied our method to investigate the consequences of perturbations upon deletion of the H3.3 chaperone HIRA. We used HIRA knockout and control cells, and compared H3.1 and H3.3 distribution to early replication patterns by EdU labeling and sequencing of nascent DNA.
Project description:Plant development is characterised by the capacity to reprogram differentiated cells to initiate asexual reproduction and to produce new organs such as lateral roots. To test whether HIRA could be involved in aspects of developmental reprogramming we studied the effect of HIRA during de-differentiation Arabidopsis root tissue was digested with enzyme to generate protoplast. This process would induce plant cell dedifferentiation. Experiments were performed in WT and hira background to understand how hira affect plant dedifferentiation process.
Project description:Age-associated functional decline is partly driven by progressive chromatin degeneration. Maintenance of chromatin integrity preserves cell identity and promotes healthy aging, but through different mechanisms in proliferating and non-proliferating cells. However, specific mechanisms of chromatin maintenance and their compensatory capacity in proliferating and non-proliferating cells are undefined. The histone chaperone HIRA deposits the histone variant H3.3 in a DNA replication-independent manner, leading to its accumulation in aging, non-proliferating cells. Here, we show that hepatocyte-specific loss of HIRA causes loss of cell identity, metabolic dysfunction, and accelerated fibrotic pathology with age. Transcriptomic and epigenomic analyses indicate that HIRA-H3.3 preserves chromatin integrity and sustains transcription of highly expressed genes, including cell identity genes. Partial hepatectomy, associated with induced proliferation, restores identity of HIRA knockout livers with compensatory deposition of canonical histones H3.1/2. Together, these results demonstrate that HIRA-mediated H3.3 deposition is essential for safeguarding cell identity and tissue function during aging of non-proliferating cells, but this function can be rescued by tissue regeneration and associated cell proliferation.
Project description:The HIRA chaperone complex, comprised of HIRA, UBN1 and CABIN1, collaborates with histone-binding protein ASF1a to incorporate histone variant H3.3 into chromatin in a DNA replication-independent manner. To better understand its function and mechanism, we integrated HIRA, UBN1, ASF1a and histone H3.3 ChIP-seq and gene expression analyses. Most HIRA-binding sites co-localize with UBN1, ASF1a and H3.3 at active promoters and active and weak/poised enhancers. At promoters, binding of HIRA/UBN1/ASF1a correlates with the level of gene expression. HIRA is required for deposition of histone H3.3 at its binding sites. There are marked differences in nucleosome and co-regulator composition at different classes of HIRA-bound regulatory site. Underscoring this, we report novel physical interactions between the HIRA complex and transcription factors, a chromatin insulator and an ATP-dependent chromatin-remodelling complex. Our results map the distribution of the HIRA chaperone across the chromatin landscape and point to different interacting partners at functionally distinct regulatory sites. We used microarrays to detail the global programme of gene expression after knockdown of HIRA HeLa cells were nucleofacted with Dharmacon control siRNA and siRNA to HIRA and RNA was isolated 72 hours after transfection in four biological replicates
Project description:Age-associated functional decline is partly driven by progressive chromatin degeneration. Conversely, maintenance of chromatin integrity preserves cell identity and promotes healthy aging, albeit through different mechanisms in proliferating and non-proliferating cells. However, whether tissue regeneration with its associated cell proliferation can rescue defects in epigenetic maintenance in otherwise non-proliferative cells remains unclear. The histone chaperone HIRA deposits the histone variant H3.3 in a DNA replication–independent manner, leading to its accumulation in aging, non-proliferating cells. Here, we show that hepatocyte-specific loss of HIRA causes loss of cell identity, metabolic dysfunction, and accelerated fibrotic pathology with age. Transcriptomic and epigenomic analyses indicate that HIRA–H3.3 preserves chromatin integrity and sustains transcription of highly expressed genes. Partial hepatectomy, associated with induced proliferation, restores cell identity with compensatory deposition of canonical histones H3.1/2. Together, these results demonstrate that HIRA-mediated H3.3 deposition is essential for safeguarding cell identity and tissue function during aging of non-proliferating cells, but this function can be rescued by tissue regeneration with associated cell proliferation.
Project description:The HIRA chaperone complex, comprised of HIRA, UBN1 and CABIN1, collaborates with histone-binding protein ASF1a to incorporate histone variant H3.3 into chromatin in a DNA replication-independent manner. To better understand its function and mechanism, we integrated HIRA, UBN1, ASF1a and histone H3.3 ChIP-seq and gene expression analyses. Most HIRA-binding sites co-localize with UBN1, ASF1a and H3.3 at active promoters and active and weak/poised enhancers. At promoters, binding of HIRA/UBN1/ASF1a correlates with the level of gene expression. HIRA is required for deposition of histone H3.3 at its binding sites. There are marked differences in nucleosome and co-regulator composition at different classes of HIRA-bound regulatory site. Underscoring this, we report novel physical interactions between the HIRA complex and transcription factors, a chromatin insulator and an ATP-dependent chromatin-remodelling complex. Our results map the distribution of the HIRA chaperone across the chromatin landscape and point to different interacting partners at functionally distinct regulatory sites. We used microarrays to detail the global programme of gene expression after knockdown of HIRA
Project description:The HIRA chaperone complex, comprised of HIRA, UBN1 and CABIN1, collaborates with histone-binding protein ASF1a to incorporate histone variant H3.3 into chromatin in a DNA replication-independent manner. To better understand its function and mechanism, we integrated HIRA, UBN1, ASF1a and histone H3.3 ChIP-seq and gene expression analyses. Most HIRA-binding sites co-localize with UBN1, ASF1a and H3.3 at active promoters and active and weak/poised enhancers. At promoters, binding of HIRA/UBN1/ASF1a correlates with the level of gene expression. HIRA is required for deposition of histone H3.3 at its binding sites. There are marked differences in nucleosome and co-regulator composition at different classes of HIRA-bound regulatory site. Underscoring this, we report novel physical interactions between the HIRA complex and transcription factors, a chromatin insulator and an ATP-dependent chromatin-remodelling complex. Our results map the distribution of the HIRA chaperone across the chromatin landscape and point to different interacting partners at functionally distinct regulatory sites. Examination of 3 histone chaperone proteins in HeLa cells
Project description:Age-associated functional decline is partly driven by progressive chromatin degeneration. Conversely, maintenance of chromatin integrity preserves cell identity and promotes healthy aging, albeit through different mechanisms in proliferating and non-proliferating cells. However, whether tissue regeneration with its associated cell proliferation can rescue defects in epigenetic maintenance in otherwise non-proliferative cells remains unclear. The histone chaperone HIRA deposits the histone variant H3.3 in a DNA replication–independent manner, leading to its accumulation in aging, non-proliferating cells. Here, we show that hepatocyte-specific loss of HIRA causes loss of cell identity, metabolic dysfunction, and accelerated fibrotic pathology with age. Transcriptomic and epigenomic analyses indicate that HIRA–H3.3 preserves chromatin integrity and sustains transcription of highly expressed genes. Partial hepatectomy, associated with induced proliferation, restores cell identity with compensatory deposition of canonical histones H3.1/2. Together, these results demonstrate that HIRA-mediated H3.3 deposition is essential for safeguarding cell identity and tissue function during aging of non-proliferating cells, but this function can be rescued by tissue regeneration with associated cell proliferation.