Large domains of heterochromatin direct the formation of short mitotic chromosome loops

During mitosis chromosomes reorganise into highly compact, rod-shaped forms, thought to consist of consecutive chromatin loops around a central protein scaffold. Condensin complexes are involved in chromatin compaction, but the contribution of other chromatin proteins, DNA sequence and histone modif...

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Bibliographic Details
Published inbioRxiv
Main Authors Fitz-James, Maximilian H, Tong, Pin, Pidoux, Alison L, Ozadam, Hakan, Yang, Liyan, White, Sharon A, Dekker, Job, Allshire, Robin C
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 01.04.2020
Subjects
Centromeres
Chromatin
Chromosomes
Condensin
Deoxyribonucleic acid
DNA
Heterochromatin
Lysine
Mitosis
Nucleotide sequence
Yeast
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Summary:During mitosis chromosomes reorganise into highly compact, rod-shaped forms, thought to consist of consecutive chromatin loops around a central protein scaffold. Condensin complexes are involved in chromatin compaction, but the contribution of other chromatin proteins, DNA sequence and histone modifications is less understood. A large region of fission yeast DNA inserted into a mouse chromosome was previously observed to adopt a mitotic organisation distinct from that of surrounding mouse DNA. Here we show that a similar distinct structure is common to a large subset of insertion events in both mouse and human cells and is coincident with the presence of high levels of heterochromatic H3 lysine 9 trimethylation (H3K9me3). Hi-C and microscopy indicate that the heterochromatinised fission yeast DNA is organised into smaller chromatin loops than flanking euchromatic mouse chromatin. We conclude that heterochromatin alters chromatin loop size, thus contributing to the distinct appearance of heterochromatin on mitotic chromosomes, such as at centromeres.
DOI:10.1101/2020.04.01.019869