Suv4-20h2 mediates chromatin compaction and is important for cohesin recruitment to heterochromatin

Abstract

Cohesin plays an important role in chromatid cohesion and has additional functions in higher-order chromatin organization and in transcriptional regulation. The binding of cohesin to euchromatic regions is largely mediated by CTCF or the mediator complex. However, it is currently unknown how cohesin is recruited to pericentric heterochromatin in mammalian cells. Here we define the histone methyltransferase Suv4-20h2 as a major structural constituent of heterochromatin that mediates chromatin compaction and cohesin recruitment. Suv4-20h2 stably associates with pericentric heterochromatin through synergistic interactions with multiple heterochromatin protein 1 (HP1) molecules, resulting in compaction of heterochromatic regions. Suv4-20h mutant cells display an overall reduced chromatin compaction and an altered chromocenter organization in interphase referred to as ''chromocenter scattering.'' We found that Suv4-20h-deficient cells display chromosome segregation defects during mitosis that coincide with reduced sister chromatid cohesion. Notably, cohesin subunits interact with Suv4-20h2 both in vitro and in vivo. This interaction is necessary for cohesin binding to heterochromatin, as Suv4-20h mutant cells display substantially reduced cohesin levels at pericentric heterochromatin. This defect is most prominent in G0-phase cells, where cohesin is virtually lost from heterochromatin, suggesting that Suv4-20h2 is involved in the initial loading or maintenance of cohesion subunits. In summary, our data provide the first compelling evidence that Suv4-20h2 plays essential roles in regulating nuclear architecture and ensuring proper chromosome segregation.

SUV4-20 activity in the preimplantation mouse embryo controls timely replication

“…In addition, because H4K20 methylation is processive and is among the modifications with the slowest rate of formation (Zee et al 2010), it may take longer for SUV4-20H1 to reach full processivity in the absence of basal levels of H4K20me3 and/or H3K9me3. It is noteworthy that Suv4-20 enzymes can be targeted to chromatin through interaction with HP1, which mediates stable SUV4-20H2 binding synergistically (Schotta et al 2004;Hahn et al 2013). Because HP1β appears in the paternal chromatin only after S phase (Santos et al 2005;Santenard et al 2010) and because SUV4-20H1/H2 are known to function mostly in G1 (Zee et al 2010), the lack of HP1 on the paternal pronucleus together with the processivity nature of SUV4-20 enzymes would explain why H4K20me3 is detected in the paternal chromatin only at the two-cell stage.…”

“…It is also possible that the longer nature of SUV4-20H1, which has 406 more amino acids than SUV4-20H2, may modulate its processivity. Strong overexpression of Suv4-20h2 in embryonic stem cells leads to increased chromatin compaction around chomocenters and consequent mitotic segregation defects (Hahn et al 2013). However, we did not detect segregation defects in SUV4-20H2-expressing embryos.…”

Histone H4 Lysine 20 (H4K20) Methylation, Expanding the Signaling Potential of the Proteome One Methyl Moiety at a Time

“…However, H3K9me3 signals persist at DAPIdense foci in cells in the absence of SUV4-20H1 and SUV4-20H2. Interestingly the C-terminal domain of SUV4-20H2 can bind to isoforms of HP1, key components of heterochromatin, and through their chromodomains can direct the binders of H3K9me3 (20,(42)(43)(44). This suggests a model in which H3K9me3 recruitment of HP1 brings in SUV4-20H2 to establish an H4K20me3 landscape at heterochromatin.…”

Coming to terms with chromatin structure

“…Using this method, Fan et al demonstrated that a loss of linker histone H1 leads to a decrease in nucleosomal spacing (Fan et al 2003). Digestion experiments with increasing concentrations of MNase (Hahn et al 2013) or with increasing incubation times (Gilbert et al 2007) provide diagnostic digestion patterns that have been used to imply changes in chromatin 'compaction'.…”