Chromatin assembly factor HIRA is essential for the maintenance of hematopoiesis
Ontology highlight
ABSTRACT: HIRA is a histone chaperone that deposits the histone variant H3.3 in transcriptionally active genes. HIRA is essential for mouse development, as the standard knockout (KO) results in early embryonic death. However, the role of HIRA in hematopoiesis is poorly understood. We investigated the effect of Hira KO on hematopoiesis using Vav-Cre Loxp system. We show that Hira KO dramatically reduces bone marrow LSK cells, resulting in anemia, thrombopenia and severe, combined immunodeficiency. To investigate the molecular mechanisms, RNA-seq and ATAC-Seq were performed using LSK cells isolated from WT and Hira conditional KO mice.
Project description:Cellular senescence is a stable proliferation arrest that suppresses tumorigenesis. Histone chaperone HIRA deposits nucleosome-destabilizing histone variant H3.3 into chromatin in a DNA replication-independent manner. Histone H3.3 and a subset of other typically M-bM-^@M-^\replication-dependentM-bM-^@M-^] core histones were expressed in non-proliferating senescent cells, the latter linked to alternative mRNA splicing and polyadenylation. Senescent cells incorporated newly-synthesized histones into chromatin, partially dependent on HIRA. HIRA and newly-deposited histone H3.3 co-localized at promoters of expressed genes, and their distribution shifted between proliferating and senescent cells, paralleling changes in gene expression. In senescent cells, gene promoters showed exceptional enrichment of a histone acetylation linked to open and dynamic chromatin, H4K16ac. Abundance of H4K16ac depended on HIRA. In the mouse, inactivation of HIRA downregulated H4K16ac and dramatically enhanced oncogene-induced hyperplasia. To conclude, HIRA controls a previously undefined dynamic non-canonical H4K16ac-decorated chromatin landscape in senescence, and also plays an unanticipated role in suppression of oncogene-induced neoplasia. Examination of HIRA protein binding alongside histone modification H4K16ac and H3.3 in proliferating and senescent IMR90 cells
Project description:The mammalian HIRA/UBN1/ASF1a complex is a histone chaperone complex that is conserved from yeast (Saccharomyces cerevisiae) to humans. This complex preferentially deposits the histone variant H3.3 into chromatin in a DNA replication-independent manner and is implicated in diverse chromatin regu- latory events from gene activation to heterochromatinization. In yeast, the orthologous complex consists of three Hir proteins (Hir1p, Hir2p, and Hir3p), Hpc2p, and Asf1p. Yeast Hir3p has weak homology to CABIN1, a fourth member of the human complex, suggesting that Hir3p and CABIN1 may be orthologs. Here we show that HIRA and CABIN1 interact at ectopic and endogenous levels of expression in cells, and we isolate the quaternary HIRA/UBN1/CABIN1/ASF1a (HUCA) complex, assembled from recombinant proteins. Mutational analyses support the view that HIRA acts as a scaffold to bring together UBN1, ASF1a, and CABIN1 into a quaternary complex. We show that, like HIRA, UBN1, and ASF1a, CABIN1 is involved in heterochromatinization of the genome of senescent human cells. Moreover, in proliferating cells, HIRA and CABIN1 regulate overlapping sets of genes, and these genes are enriched in the histone variant H3.3. In sum, these data demonstrate that CABIN1 is a functional member of the human HUCA complex and so is the likely ortholog of yeast Hir3p. We used microarrays to detail the global programme of gene expression after knockdown of HIRA and CABIN1 in 3 replicates HeLa cells were nucleofacted with Dharmacon control siRNA and siRNA to HIRA and CABIN1 and RNA was isolated 72 hours after transfection.
Project description:Cellular senescence is a stable proliferation arrest that suppresses tumorigenesis. Histone chaperone HIRA deposits nucleosome-destabilizing histone variant H3.3 into chromatin in a DNA replication-independent manner. Histone H3.3 and a subset of other typically “replication-dependent” core histones were expressed in non-proliferating senescent cells, the latter linked to alternative mRNA splicing and polyadenylation. Senescent cells incorporated newly-synthesized histones into chromatin, partially dependent on HIRA. HIRA and newly-deposited histone H3.3 co-localized at promoters of expressed genes, and their distribution shifted between proliferating and senescent cells, paralleling changes in gene expression. In senescent cells, gene promoters showed exceptional enrichment of a histone acetylation linked to open and dynamic chromatin, H4K16ac. Abundance of H4K16ac depended on HIRA. In the mouse, inactivation of HIRA downregulated H4K16ac and dramatically enhanced oncogene-induced hyperplasia. To conclude, HIRA controls a previously undefined dynamic non-canonical H4K16ac-decorated chromatin landscape in senescence, and also plays an unanticipated role in suppression of oncogene-induced neoplasia.
Project description:The mammalian HIRA/UBN1/ASF1a complex is a histone chaperone complex that is conserved from yeast (Saccharomyces cerevisiae) to humans. This complex preferentially deposits the histone variant H3.3 into chromatin in a DNA replication-independent manner and is implicated in diverse chromatin regu- latory events from gene activation to heterochromatinization. In yeast, the orthologous complex consists of three Hir proteins (Hir1p, Hir2p, and Hir3p), Hpc2p, and Asf1p. Yeast Hir3p has weak homology to CABIN1, a fourth member of the human complex, suggesting that Hir3p and CABIN1 may be orthologs. Here we show that HIRA and CABIN1 interact at ectopic and endogenous levels of expression in cells, and we isolate the quaternary HIRA/UBN1/CABIN1/ASF1a (HUCA) complex, assembled from recombinant proteins. Mutational analyses support the view that HIRA acts as a scaffold to bring together UBN1, ASF1a, and CABIN1 into a quaternary complex. We show that, like HIRA, UBN1, and ASF1a, CABIN1 is involved in heterochromatinization of the genome of senescent human cells. Moreover, in proliferating cells, HIRA and CABIN1 regulate overlapping sets of genes, and these genes are enriched in the histone variant H3.3. In sum, these data demonstrate that CABIN1 is a functional member of the human HUCA complex and so is the likely ortholog of yeast Hir3p. We used microarrays to detail the global programme of gene expression after knockdown of HIRA and CABIN1 in 3 replicates
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: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: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.
Project description:In this study, we demonstrate that the UBN1 or UBN2 subunit is mainly responsible for specific recognition and direct binding of H3.3 by the HIRA complex, while the HIRA subunit can enhance the binding affinity of UBN1 toward H3.3, but Cabin1 subunit cannot. We also demonstrate that both Ala87 and Gly90 residues of H3.3 are required and sufficient for the specific recognition and binding by UBN1. ChIP-seq studies reveal that two independent HIRA complexes (UBN1-HIRA and UBN2-HIRA) can cooperatively deposit H3.3 to cis-regulatory regions, including active promoters and active enhancers in mouse embryonic stem (mES) cells. Importantly, disruption of histone chaperone activities of UBN1 and UBN2 by FID/AAA mutation results in the defect of H3.3 deposition at promoters of developmental genes involved in neural differentiation, and subsequently causes the failure of activation of these genes during neural differentiation of mES cells. Together, our results provide novel insights into the mechanism by which the HIRA complex specifically recognizes and deposits H3.3 at promoters and enhancers of developmental genes, which plays a critical role in neural differentiation of mES cells
Project description:In this study, we demonstrate that the UBN1 or UBN2 subunit is mainly responsible for specific recognition and direct binding of H3.3 by the HIRA complex, while the HIRA subunit can enhance the binding affinity of UBN1 toward H3.3, but Cabin1 subunit cannot. We also demonstrate that both Ala87 and Gly90 residues of H3.3 are required and sufficient for the specific recognition and binding by UBN1. ChIP-seq studies reveal that two independent HIRA complexes (UBN1-HIRA and UBN2-HIRA) can cooperatively deposit H3.3 to cis-regulatory regions, including active promoters and active enhancers in mouse embryonic stem (mES) cells. Importantly, disruption of histone chaperone activities of UBN1 and UBN2 by FID/AAA mutation results in the defect of H3.3 deposition at promoters of developmental genes involved in neural differentiation, and subsequently causes the failure of activation of these genes during neural differentiation of mES cells. Together, our results provide novel insights into the mechanism by which the HIRA complex specifically recognizes and deposits H3.3 at promoters and enhancers of developmental genes, which plays a critical role in neural differentiation of mES cells