lo 4 PcG in chromatin organisation

[?] How is PcG involved in chromatin compaction?

It was discovered in 2004 that PRC1 complexes were sufficient to compact nucleosomal arrays in vitro.

[?] What are Polycomb bodies?

condensed nuclear speckles containing PcG complexes and many PcG repressed loci.

what do polycomb bodies

represent

a higher-order organisation of PcG-mediated repression in the nucleus.

[?] What is the role of PHC1 and PHC2 in Polycomb body formation?

involved in maintaining long-range genome contacts

through hetero-oligomerisation of PHC molecules

at different sites in the genome.

What do PHC1 and PHC2 in Polycomb body contribute to

These long-range links contribute to the formation of Polycomb bodies.

[?] What happens to Polycomb bodies in PHC1 mutants?

Hi-C experiments show that PHC1 mutants lose Polycomb body formation at target loci

[?] What happens to Polycomb bodies in PHC1 mutants?

example

(such as HOXA in the example given),

[?] What happens to Polycomb bodies in PHC1 mutants?

demonstrating that phc1 is

essential for maintaining long-range contacts between PcG target sites.

[?] What are the levels of 3D genome organisation?

DNA double helix,

nucleosomes,

chromatin fibre,

loops

topologically associating domains (TADs),

chromosome territories.

[?] How does PRC1 contribute to genome architecture?

PRC1 is essential to maintain contacts between PcG target sites.

PRC1-mediated compaction and long-range interactions are key aspects.

[?] What technique is used to study long-range genomic contacts?

Hi-C (High-throughput Chromosome Conformation Capture)

hi c

has been instrumental in showing that

PHC1 mutants lose Polycomb body formation