The Integrity of the Speciation Core Complex is necessary for centromeric binding and reproductive isolation inDrosophila

Abstract

Postzygotic isolation by genomic conflict is a major cause for the formation of species. Despite its importance, the molecular mechanisms that result in the lethality of interspecies hybrids are still largely unclear. The genus Drosophila, which contains over 1600 different species, is one of the best characterized model systems to study these questions. We showed in the past that the expression levels of the two hybrid incompatibility factors Hmr and Lhr diverged in the two closely related Drosophila species, D. melanogaster and D. simulans, resulting in an increased level of both proteins in interspecies hybrids. This overexpression leads to mitotic defects, a misregulation in the expression of transposable elements and a decreased fertility. In this work, we describe a distinct six subunit Speciation Core Complex (SCC) containing HMR and LHR and analyse the effect of Hmr mutations on complex function and integrity. Our experiments suggest that HMR acts as a bridging factor between centromeric chromatin and pericentromeric heterochromatin, which is required for both its physiological function and its ability to cause hybrid male lethality.

Multi-tissue proteomics identifies a link between satellite DNA organization and transgenerational transposon repression inDrosophila

“…S3B, E). Similarly, the D1-interacting heterochromatin protein, Hmr, which contributes to TE repression, was also observed at the chromocenter boundary, in agreement with recent reports suggesting that Hmr may bridge centromeric and pericentromeric heterochromatin [24,27] (Fig. S3C, F).…”

“…The copyright holder for this preprint this version posted July 12, 2023. ; https://doi.org/10.1101/2023.07.11.548599 doi: bioRxiv preprint proteins [23][24][25] or centromeric proteins [24,26,27]. In addition, these studies have largely been performed in cultured cells and we still lack detailed knowledge of the heterochromatin-associated proteome in intact tissues.…”

Defective Satellite DNA Clustering into Chromocenters Underlies Hybrid Incompatibility in Drosophila

“…Previous work from other groups have shown that Hmr and Lhr can localize to chromocenters ( Brideau et al 2006 ; Satyaki et al 2014 ; Kochanova et al 2020 ) and exhibit increased expression levels in lethal male hybrids ( Thomae et al 2013 ). Moreover, Hmr and Lhr colocalize/form complexes with Gfzf in both pure species and hybrids ( Cooper et al 2019 ; Lukacs et al 2021 ). We therefore speculate that a complex of HI factors in hybrids could inhibit either the protein–DNA or protein–protein interactions that contribute to chromocenter formation ( fig.…”