The molecular architecture of CenH3-deficient holocentromeres in Lepidoptera is dependent on transcriptional and chromatin dynamics

Abstract

<jats:p>Despite their essentiality for chromosome segregation, centromeres are diverse among eukaryotes and embody two main configurations: mono- and holocentromeres, referring respectively to a localized or unrestricted distribution of centromeric activity. Previous studies revealed that holocentricity in many insects coincides with the loss of the otherwise essential centromere component CenH3 (CENP-A), suggesting a molecular link between the two events. In this study, we leveraged recently-identified centromere components to map and characterize the centromeres of Bombyx mori. This uncovered a robust correlation between centromere profiles and regions of low chromatin dynamics. Transcriptional perturbation experiments showed that low chromatin activity is crucial for centromere formation in B. mori. Our study points to a novel mechanism of centromere formation that occurs in a manner recessive to the chromosome-wide chromatin landscape. Based on similar profiles in additional Lepidoptera, we propose an evolutionarily conserved mechanism that underlies the establishment of holocentromeres through loss of centromere specificity.</jats:p>

Centromeric Transcription: A Conserved Swiss-Army Knife

“…A key missing part of the puzzle is whether centromeric transcription also occurs in holocentric species. Work on the nematode Caenorhabditis elegans [ 82 ] and lepidopteran Bombyx mori [ 83 ] indicate anti-correlations between active transcription and the localizations of CENP-A and CENP-T chromatin, respectively. These data were obtained in asynchronized cells, which might not reveal low-level transcription at centromeric chromatin.…”