Structural mechanisms of DREAM complex assembly and regulation

Abstract

The DREAM complex represses cell cycle genes during quiescence through scaffolding MuvB proteins with E2F4/5 and the Rb tumor suppressor paralog p107 or p130. Upon cell cycle entry, MuvB dissociates from p107/p130 and recruits B-Myb and FoxM1 for up-regulating mitotic gene expression. To understand the biochemical mechanisms underpinning DREAM function and regulation, we investigated the structural basis for DREAM assembly. We identified a sequence in the MuvB component LIN52 that binds directly to the pocket domains of p107 and p130 when phosphorylated on the DYRK1A kinase site S28. A crystal structure of the LIN52-p107 complex reveals that LIN52 uses a suboptimal LxSxExL sequence together with the phosphate at nearby S28 to bind the LxCxE cleft of the pocket domain with high affinity. The structure explains the specificity for p107/p130 over Rb in the DREAM complex and how the complex is disrupted by viral oncoproteins. Based on insights from the structure, we addressed how DREAM is disassembled upon cell cycle entry. We found that p130 and B-Myb can both bind the core MuvB complex simultaneously but that cyclin-dependent kinase phosphorylation of p130 weakens its association. Together, our data inform a novel target interface for studying MuvB and p130 function and the design of inhibitors that prevent tumor escape in quiescence.

MYBL2 is a Potential Prognostic Marker that Promotes Cell Proliferation in Gallbladder Cancer

“…In contrast, MYBL2 overexpression induced S phase cell cycle increase, which simultaneously might induce the G2-to-M cell cycle transition. The results are consistent with previous studies showing that MYBL2 together with MuvB and FoxM1 regulated the expression of several key genes required for the G2/M transition [12, 16, 35]. …”

“…Upon cell cycle entry, the MuvB core dissociates from P107/P130 and sequentially recruits MYBL2 and FoxM1 to coordinate the expression of the late cell cycle G2/M genes. The expression of MYBL2, which is involved in cell cycle regulation and performs essential functions in proliferating cells, is hardly detectable at G0 phase and is induced at the G1/S transition of the cell cycle [10-16]. MYBL2 is overexpressed in several types of tumours, including hepatocellular carcinoma, lung cancer, breast cancer, cervical cancer and colorectal cancer [17-24].…”

Structural Conservation and E2F Binding Specificity within the Retinoblastoma Pocket Protein Family

“…1) [23–25]. p107 and p130 also bind viral and chromatin factors through their LxCxE cleft, and they use this cleft to bind LIN52 in the DREAM complex [10, 26]. It has been observed in cells that p107/p130 binds E2F4 and E2F5 but not E2F1, E2F2, and E2F3, while Rb is found bound to E2F1 through E2F5 [27].…”

Phosphorylation of transcriptional regulators in the retinoblastoma protein pathway by UL97, the viral cyclin-dependent kinase encoded by human cytomegalovirus

“…Expression plasmids have been described: pCGN-HA UL97wt and pCGN-HA UL97kd, (Kuny et al, 2010); Rc/cyclin A2 and Rc/cyclin E1 (Hinds et al, 1992); Rc/cyclin D2 (Baker et al, 2005); CMV-CDK4 (van den Heuvel and Harlow, 1993); LIN52-V5-pEF6 (Guiley et al, 2015); pCMV-T7-FoxM1B (Chen et al, 2009); pCMV-DP1 (Helin et al, 1993); pE2F1-Luc(-242) (Johnson et al, 1994); pCMV-Rb (Qin et al, 1992). pCDK2-HA, pUHD-CDK1-WT-HA, p-cyclin B1-mCherry, pCMV-Neo-Bam-E2F3a and pCMV-Neo-Bam-E2F3b were purchased from Addgene (#1884, #27652, #26063, #37970 and #37975) (Gavet and Pines, 2010; Lees et al, 1993; van den Heuvel and Harlow, 1993).…”

“…The MuvB component LIN52 binds directly to p107 and p130 through an LXCXE-like motif. Phosphorylation of a nearby serine residue (Ser28) on LIN52 by the DYRK1A kinase is required for binding to p107 and p130 (Guiley et al, 2015; Litovchick et al, 2011). Progression through the G1 and S phases is controlled by Rb in complex with E2F1, E2F2, E2F3a, E2F3b and E2F4 (Dyson, 1998).…”