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Umbrea, a chromo shadow domain protein in Drosophila melanogaster heterochromatin, interacts with Hip, HP1 and HOAP.

ABSTRACT: Drosophila melanogaster HP1-interacting protein (Hip) is a partner of heterochromatin protein 1 (HP1) and is involved in transcriptional epigenetic gene silencing and the formation of heterochromatin. Recently, it has been shown that HP1 interacts with the telomere capping factor HP1/ORC (origin recognition complex)-associated protein (HOAP). Telomeres, complexes of DNA and proteins at the end of linear chromosomes, have been recognized to protect chromosome ends from degradation and fusion events. Both proteins are located at telomeres and prevent telomere fusions. Here, we report the identification and characterization of the Hip-interacting protein Umbrea. We found that Umbrea interacts directly with Hip, HP1 and HOAP in vitro. Umbrea, Hip and HP1 are partners in a protein complex in vivo and completely co-localize in the pericentric heterochromatin and at telomeres. Using a Gal4-induced RNA interference system, we found that after depletion of Umbrea in salivary gland polytene chromosomes, they exhibit multiple telomeric fusions. Taken together, these results suggest that Umbrea cooperates with Hip, HP1 and HOAP and plays a functional role in mediating normal telomere behaviour in Drosophila.

SUBMITTER: Joppich C

PROVIDER: S-EPMC2758380 | biostudies-other | 2009

REPOSITORIES: biostudies-other

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Project description:The replication of a genomic region during S-phase can be highly dynamic between cell types that differ in transcriptome and epigenome. Replication timing has been positively correlated with several histone modifications that occur at active genes, while repressive histone modifications mark late replicating regions. This raises the question if chromatin modulates the initiating events of replication. To gain insights into this question we have studied the function of heterochromatin protein 1 (HP1), a reader of to the repressive histone lysine 9 methylation of H3, in genome-wide organization of replication. Cells with reduced levels of HP1 show an advanced replication timing of centromeric repeats in agreement with the model that repressive chromatin mediates the very late replication of large clusters of constitutive heterochromatin. Surprisingly however regions with high levels of interspersed repeats on the chromosomal arms in particular on chromosome 4 and in pericentromeric regions of chromosome 2 behave differently. Here loss of HP1 results in delayed replication timing. The fact that these regions are bound by HP1 suggests a direct effect. Thus while HP1 mediates very late replication of centromeric DNA it is also required for early replication of autosomal regions with high levels of repeats. This observation of opposing functions of HP1 suggests a model where repeat inactivation on autosomes is required for proper activation of origins of replication that fire early, while HP1 mediated repression at constitutive heterochromatin is required to ensure replication of centromeric repeats at the end of S phase. Keywords: RNAi, chip-chip, replication timing

2010-03-16 | GSE18092 | GEO

Phylogenomic analysis reveals dynamic evolutionary history of the Drosophila heterochromatin protein 1 (HP1) gene family.

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