Pericentric heterochromatin state during the cell cycle controls the histone variant composition of centromeres

Abstract

BSTRACTCorrect chromosome segregation requires a unique chromatin environment at centromeres and in their vicinity. Here, we address how the deposition of canonical H2A and H2A.Z histone variants is controlled at pericentric heterochromatin (PHC). Whereas in euchromatin newly synthesized H2A and H2A.Z are deposited throughout the cell cycle, we reveal two discrete waves of deposition at PHC -during mid to late S phase in a replicationdependent manner for H2A and during G1 phase for H2A.Z. This G1 cell cycle restriction is lost when heterochromatin features are altered, leading to the accumulation of H2A.Z at the domain. Interestingly, compromising PHC integrity also impacts upon neighboring centric chromatin, increasing the amount of centromeric CENP-A without changing the timing of its deposition. We conclude that the higher-order chromatin structure at the pericentric domain influences dynamics at the nucleosomal level within centromeric chromatin. The two different modes of rearrangement of the PHC during the cell cycle provide distinct opportunities to replenish one or the other H2A variant, highlighting PHC integrity as a potential signal to regulate the deposition timing and stoichiometry of histone variants at the centromere.

Condensin Promotes Position Effects within Tandem DNA Repeats via the RITS Complex

“…Indeed, RNAi components and Clr4 have been shown to be required for establishment of CENP-A cnp1 chromatin at centromere in fission yeast (Folco et al, 2008; Gonzalez et al, 2014). Previous studies also demonstrate that peri-centromeric heterochromatin is important for centromeric localization of CENP-A in Neurospora crassa and mouse cell lines (Boyarchuk et al, 2014; Smith et al, 2011). Here, we show that the key regulator of the position effect in pericentromeric repeats, Cut3, is also required for the centromeric localization of CENP-A cnp1 (Figure 4F).…”

“…The peri-centromeric heterochromatin has been linked to centromere function and chromosome segregation (Boyarchuk et al, 2014; Folco et al, 2008; Gonzalez et al, 2014; Smith et al, 2011). …”

Polycomb RING1A/RING1B-dependent histone H2A monoubiquitylation at pericentromeric regions promotes S phase progression

“…INO80 activity in DNA replication, however, seems to be rather general, meaning it is unlikely to mediate a PCH-specific replication defect. A more-appealing candidate is S-phase-stagespecific deposition of histone H2A, as has been recently discovered (Boyarchuk et al, 2014). Nucleosomal density during replication is maintained by recycling of parental histones together with the incorporation of newly synthesised histones, and the efficiency of this process influences fork progression (Groth et al, 2007;Jasencakova et al, 2010;Mejlvang et al, 2014).…”

“…Nucleosomal density during replication is maintained by recycling of parental histones together with the incorporation of newly synthesised histones, and the efficiency of this process influences fork progression (Groth et al, 2007;Jasencakova et al, 2010;Mejlvang et al, 2014). Of note is that, whereas in euchromatin the deposition of newly synthesised histone H2A occurs throughout the cell cycle, at PCH it is a strictly replication-dependent process (Boyarchuk et al, 2014). Perhaps, this temporally restricted deposition of H2A at PCH is linked to nucleosomal reconstitution and chromatin maturation processes accompanying transient structural changes at the periphery of PCH domains where DNA replication actually takes place (Quivy et al, 2004).…”

Essential role for centromeric factors following p53 loss and oncogenic transformation

“…Reverse transcription and qPCR were carried out as described previously (Boyarchuk et al 2014). Real-time qPCRs were performed on an ABI PRISM 7500 using Power SYBR Green (Applied Biosystems).…”