Dataset: lhp1 FLC-Venus time course imaging – Hybrid protein assembly-histone modification mechanism for PRC2-based epigenetic switching and memory

The histone modification H3K27me3 plays a central role in
Polycomb-mediated epigenetic silencing. H3K27me3 recruits and
allosterically activates Polycomb Repressive Complex 2 (PRC2), which adds
this modification to nearby histones, providing a read/write mechanism for
inheritance through DNA replication. However, for some PRC2 targets, a
purely histone-based system for epigenetic inheritance may be
insufficient. We address this issue at the Polycomb target Flowering Locus
C (FLC) in Arabidopsis thaliana, as a narrow nucleation region of only
~three nucleosomes within FLC mediates epigenetic state switching and
subsequent memory over many cell cycles. To explain the memory’s
unexpected persistence, we introduce a mathematical model incorporating
extra protein memory storage elements with positive feedback that persist
at the locus through DNA replication, in addition to histone
modifications. Our hybrid model explains many features of epigenetic
switching/memory at FLC and encapsulates generic mechanisms that may be
widely applicable.