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Heterochromatic 3D genome organization is directed by HP1a and H3K9-dependent and independent mechanisms [Hi-C]

ABSTRACT: Histone post-translational modifications and the proteins that bind them are proposed to be drivers of 3D genome organization, but whether and how they do so remain unanswered. Here, we evaluate the contribution of H3K9-methylated constitutive heterochromatin to 3D genome organization in Drosophila tissues. We find that the predominant organizational feature of wildtype tissues is segregation of euchromatic chromosome arms from heterochromatic pericentromeres. Reciprocal perturbation of HP1a•H3K9 binding, using a point mutation in the HP1a chromodomain or replacement of the replication-dependent H3 with H3K9R mutant histones, revealed that HP1a binding to methylated H3K9 in constitutive heterochromatin is required to restrict long-range interactions between pericentromeres and chromosome arms. Surprisingly, self-association of pericentromeric heterochromatin is largely preserved upon disruption of HP1a•H3K9 binding despite loss of pericentromeric H3K9 methylation and HP1a occupancy. Thus, the HP1a•H3K9 interaction contributes to, but does not solely drive, segregation of euchromatin and heterochromatin inside the nucleus.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE233384 | GEO | 2024/05/24

REPOSITORIES: GEO

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Heterochromatic 3D genome organization is directed by HP1a and H3K9-dependent and independent mechanisms [RNA-seq]

Project description:Histone post-translational modifications and the proteins that bind them are proposed to be drivers of 3D genome organization, but whether and how they do so remain unanswered. Here, we evaluate the contribution of H3K9-methylated constitutive heterochromatin to 3D genome organization in Drosophila tissues. We find that the predominant organizational feature of wildtype tissues is segregation of euchromatic chromosome arms from heterochromatic pericentromeres. Reciprocal perturbation of HP1a•H3K9 binding, using a point mutation in the HP1a chromodomain or replacement of the replication-dependent H3 with H3K9R mutant histones, revealed that HP1a binding to methylated H3K9 in constitutive heterochromatin is required to restrict long-range interactions between pericentromeres and chromosome arms. Surprisingly, self-association of pericentromeric heterochromatin is largely preserved upon disruption of HP1a•H3K9 binding despite loss of pericentromeric H3K9 methylation and HP1a occupancy. Thus, the HP1a•H3K9 interaction contributes to, but does not solely drive, segregation of euchromatin and heterochromatin inside the nucleus.

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Project description:Whether and how histone post-translational modifications and the proteins that bind them drive 3D genome organization remains unanswered. Here, we evaluate the contribution of H3K9-methylated constitutive heterochromatin to 3D genome organization in Drosophila tissues. We find that the predominant organizational feature of wildtype tissues is segregation of euchromatic chromosome arms from heterochromatic pericentromeres. Reciprocal perturbation of HP1a•H3K9me binding, using a point mutation in the HP1a chromodomain or replacement of the replication-dependent histone H3 with H3K9R mutant histones, revealed that HP1a binding to methylated H3K9 in constitutive heterochromatin is required to limit contact frequency between pericentromeres and chromosome arms and regulate the distance between arm and pericentromeric regions. Surprisingly, self-association of pericentromeric regions is largely preserved despite loss of H3K9 methylation and HP1a occupancy. Thus, the HP1a•H3K9 interaction contributes to, but does not solely drive, segregation of euchromatin and heterochromatin inside the nucleus.

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HP1a recruitment to promoters is independent of H3K9 methylation in Drosophila melanogaster

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Chromatin conformation and transcriptional activity are permissive regulators of DNA replication initiation in Drosophila

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