Intricate structure of the interphase chromocenter revealed by proximity based biotinylation

During interphase centromeres often coalesce into a small number of chromocenters, which can be visualized as distinct, DAPI dense nuclear domains. Intact chromocenters play a major role in maintaining genome stability as they stabilize the transcriptionally silent state of repetitive DNA while ensuring centromere function. Despite its biological importance, relatively little is known about the molecular composition of the chromocenter or the processes that mediate chromocenter formation and maintenance. To shed light on this, we performed confocal and super resolution microscopy and proximity based biotinylation experiments of three proteins associated with the chromocenter in Drosophila: the centromeric H3 variant dCenpA, the heterochromatin protein HP1a and the speciation factor HMR. Our work revealed an intricate internal structure of the chromocenter suggesting a complex multilayered structure of this intranuclear domain. ChIP-seq experiments of HMR ChIP in dCenpC knock-down (RNAi) and control (GST RNAi) as well as CAPH2 ChIP in HMR+LHR over-expression (induced) and control induced condition in 2 biological replicates.