Dynamic regulation of the PR-Set7 histone methyltransferase is required for normal cell cycle progression

Abstract

Although the PR-Set7/Set8/KMT5a histone H4 Lys 20 monomethyltransferase (H4K20me1) plays an essential role in mammalian cell cycle progression, especially during G2/M, it remained unknown how PR-Set7 itself was regulated. In this study, we discovered the mechanisms that govern the dynamic regulation of PR-Set7 during mitosis, and that perturbation of these pathways results in defective mitotic progression. First, we found that PR-Set7 is phosphorylated at Ser 29 (S29) specifically by the cyclin-dependent kinase 1 (cdk1)/cyclinB complex, primarily from prophase through early anaphase, subsequent to global accumulation of H4K20me1. While S29 phosphorylation did not affect PR-Set7 methyltransferase activity, this event resulted in the removal of PR-Set7 from mitotic chromosomes. S29 phosphorylation also functions to stabilize PR-Set7 by directly inhibiting its interaction with the anaphase-promoting complex (APC), an E3 ubiquitin ligase. The dephosphorylation of S29 during late mitosis by the Cdc14 phosphatases was required for APC cdh1 -mediated ubiquitination of PR-Set7 and subsequent proteolysis. This event is important for proper mitotic progression, as constitutive phosphorylation of PR-Set7 resulted in a substantial delay between metaphase and anaphase. Collectively, we elucidated the molecular mechanisms that control PR-Set7 protein levels during mitosis, and demonstrated that its orchestrated regulation is important for normal mitotic progression.[Keywords: PR-Set7; APC; Cdk1; Cdc14; cell cycle; chromatin] Supplemental material is available at http://www.genesdev.org.

Epigenetic inheritance: Uncontested?

“…This was confirmed by an independent study [52]. These results are consistent with the findings that H4K20me2-3, established by the Suv4-20 enzymes, requires H4K20me1 [53], which is catalyzed by PR-Set7, whose expression is cell cycle-regulated and present from G2 to early G1 [54][55][56][57][58].…”

CDK1-dependent Inhibition of the E3 Ubiquitin Ligase CRL4CDT2 Ensures Robust Transition from S Phase to Mitosis

“…At least three substrates (CDT1, p21, and SET8) have known roles in mitosis (21)(22)(23)64), and it is possible that other CRL4 CDT2 substrates also have mitotic roles, making general substrate stabilization important for mitosis. Independent of these mitotic roles, the known substrates of replication-cou-FIGURE 6.…”

“…Depleting SET8 from asynchronous cells leads to multiple defects, including not only inefficient origin licensing in G 1 but also impaired chromatin condensation in mitosis. Thus far, these phenotypes have all been attributed to the loss of SET8-deposited histone H4K20me1 (3,23,62). However, it is not yet known whether the mitotic defects from SET8 depletion are due to the absence of SET8 specifically during G 2 and mitosis or if they arise secondarily from the absence of SET8 in a prior cell cycle phase, such as G 1 .…”

“…1). Importantly, CDT1, p21, and SET8 also function during mitosis, making their reaccumulation critical for normal mitotic progression (21)(22)(23). Replication-coupled destruction is triggered by the ubiquitin E3 ligase, CRL4…”

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

“…These observations suggested that the changes in H4K20me1 are due to parallel cell cycle changes in SETD8 protein levels. In this regard, SETD8 was found to be degraded in late G 1 -phase by the proteasome through CRL4 Cdt2 ubiquitin-mediated destruction (45)(46)(47)(48)(49)(50). Like several other cell cycle-regulated proteins, SETD8 carries two PCNA-interacting protein domains (51).…”