Mitotic Chromosome Coating Spheres, MiCCS: Distinguished components of RNA molecules surrounding mitotic chromosomes in mammalian cells

Recently, RNA molecules in mammalian cells have been extensively studied, but their role in mitosis is not fully understood because of the mitotic repression of transcription, that is, the repression of transcripts from mitotic chromosomes. Several studies have identified the distribution and function of RNA molecules in mitosis; however, the relationships between RNA molecules and condensed chromosomes during mitosis have not been systematically studied. In this study, we investigat-ed specific RNA molecules during mitosis and identified structural components that surround the chromosomes, called Mitotic Chromosome Coating Spheres (MiCCS), by using an in-cell deproteinization assay. Furthermore, we observed the unique distribution patterns of the RNA molecules—in terms of mitotic chromosomes, MiCCS, mitotic cytoplasm, and outer membranes of mitotic cells—by using a mitotic three-dimensional RNA fluorescent in situ hybridization (3D-RNA-FISH). These data provide us with a novel perspective of the relationships between RNA molecules and mitotic chromosomes.