Project description:The H3K4 methyltransferase SETD1A plays a crucial role in leukemia cell survival through its non-catalytic FLOS domain-mediated recruitment of cyclin K and regulation of DNA damage response genes. In this study, we identify a functional nuclear localization signal in and interaction partners of the FLOS domain. Our screen for FLOS domain-binding partners reveals that the SETD1A FLOS domain binds mitosis-associated proteins BuGZ/BUB3. Inhibition of both cyclin K and BuGZ/BUB3 binding motifs in SETD1A shows synergistic anti-leukemic effects. BuGZ/BUB3 localize to SETD1A-bound promoter-TSS regions and SETD1A-negative H3K4me1-positive enhancer regions adjacent to SETD1A target genes. The GLEBS motif and intrinsically disordered region of BuGZ are required for both SETD1A binding and leukemia cell proliferation. Cell-cycle specific SETD1A restoration assays indicate that SETD1A expression at the G1/S phase of the cell cycle promotes both the expression of DNA damage response genes and cell cycle progression in leukemia cells.
Project description:The H3K4 methyltransferase SETD1A plays a crucial role in leukemia cell survival through its non-catalytic FLOS domain mediated recruitment of cyclin K and regulation of DNA damage response genes. In this study, we identify a functional nuclear localization signal and interaction partners for the FLOS domain. Our proteomics analysis against FLOS domain-binding partners reveals that the SETD1A FLOS domain binds mitosis-associated proteins BuGZ/BUB3. Targeted inhibition of both cyclin K and BuGZ/BUB3 binding motifs on SETD1A shows synergistic anti-leukemic effects. BuGZ/BUB3 localize to SETD1A-positive promoter-TSS regions and SETD1A-negative H3K4me1-positive enhancer regions adjacent to SETD1A-target genes. The GLEBS motif and intrinsically disordered region of BuGZ are required for both SETD1A binding and the leukemia cell proliferation. Despite the role of BuGZ/BUB3 at mitotic phase, the cell-cycle specific SETD1A restoration study indicates the roles of SETD1A at G1/S phase of cell cycle. Discovery of this complex indicates the indispensable role of the SETD1A-BuGZ axis in cancer.
Project description:The H3K4 methyltransferase SETD1A plays a crucial role in leukemia cell survival through its non-catalytic FLOS domain mediated recruitment of cyclin K and regulation of DNA damage response genes. In this study, we identify a functional nuclear localization signal and interaction partners for the FLOS domain. Our proteomics analysis against FLOS domain-binding partners reveals that the SETD1A FLOS domain binds mitosis-associated proteins BuGZ/BUB3. Targeted inhibition of both cyclin K and BuGZ/BUB3 binding motifs on SETD1A shows synergistic anti-leukemic effects. BuGZ/BUB3 localize to SETD1A-positive promoter-TSS regions and SETD1A-negative H3K4me1-positive enhancer regions adjacent to SETD1A-target genes. The GLEBS motif and intrinsically disordered region of BuGZ are required for both SETD1A binding and the leukemia cell proliferation. Despite the role of BuGZ/BUB3 at mitotic phase, the cell-cycle specific SETD1A restoration study indicates the roles of SETD1A at G1/S phase of cell cycle. Discovery of this complex indicates the indispensable role of the SETD1A-BuGZ axis in cancer.
Project description:SETD1A, a Set1/COMPASS family member maintaining histone-H3-lysine-4 (H3K4) methylation on transcriptionally active promoters, is overexpressed in breast cancer. Here, we show that SETD1A supports mitotic processes and consequentially, its knockdown induces senescence. SETD1A, through promoter H3K4 methylation, regulates several genes orchestrating mitosis and DNA-damage responses, and its depletion causes chromosome misalignment and segregation defects. Cell cycle arrest in SETD1A knockdown senescent cells is independent of mutations in p53, RB and p16, known senescence mediators; instead, it is sustained through transcriptional suppression of SKP2, which degrades p27 and p21. Rare cells escaping senescence by restoring SKP2 expression display genomic instability. In > 200 cancer cell lines and in primary circulating tumor cells, SETD1A expression correlates with genes promoting mitosis and cell cycle suggesting a broad role in suppressing senescence induced by aberrant mitosis. Thus, SETD1A is essential to maintain mitosis and proliferation and its suppression unleashes the tumor suppressive effects of senescence.
Project description:Although studies suggest that perturbing mitotic progression leads to DNA damage and p53 activation, which in turn lead to either cell apoptosis or senescence, it remains unclear how mitotic defects trigger p53 activation. We show that BuGZ and Bub3, which are two mitotic regulators localized in the interphase nucleus, interact with the splicing machinery and are required for pre-mRNA splicing. Similar to inhibition of RNA splicing by pladienolide B, depletion of either BuGZ or Bub3 led to increased formation of RNA-DNA hybrids (R-loops), which led to DNA damage and p53 activation in both human tumor cells and primary cells. Thus, R-loop-mediated DNA damage and p53 activation offer a mechanistic explanation for apoptosis of cancer cells and senescence of primary cells upon disruption of the dual-function mitotic regulators. This demonstrates the importance of understanding the full range of functions of mitotic regulators to develop antitumor drugs.
Project description:BACKGROUND:Chromatin modification at mitosis is closely related to transcriptional reactivation in the subsequent cell cycle. We reasoned this process is deregulated by oncogenic signals, which would contribute to mitotic stress resistance in pancreatic cancer. Here, we show DMAP1/Bub3 complex mediates mitotic stress-induced cellular apoptosis, while this effect is counteracted by c-Src in pancreatic cancer cells. Our study aims to uncover an unidentified mechanism underlying the distinct response to mitotic stress between normal cells and pancreatic cancer cells. METHODS:The interaction between Bub3 and DMAP1 upon mitotic stress signaling was determined through molecular and cell biological methods. The inhibitory effect of c-Src on DMAP1/Bub3-mediated DNA methylation and gene transcription profile was investigated. The association between c-Src-mediated DMAP1 phosphorylation and paclitaxel activity in vivo and clinicopathologic characteristics were analyzed. RESULTS:Mitotic arrest induced p38-dependent phosphorylation of Bub3 at Ser211, which promotes DMAP1/Bub3 interaction. DMAP1/Bub3 complex is recruited by TAp73 to the promoter of anti-apoptotic gene BCL2L1, thus mediates the DNA methylation and represses gene transcription linked to cell apoptosis. Meanwhile, DMAP1 was highly phosphorylated at Tyr 246 by c-Src in pancreatic cancer cells, which impedes DMAP1/Bub3 interaction and the relevant cellular activites. Blocking DMAP1 pTyr-246 potentiates paclitaxel-inhibited tumor growth. Clinically, DMAP1 Tyr 246 phosphorylation correlates with c-Src activity in human pancreatic cancer specimens and poor prognosis in pancreatic cancer patients. CONCLUSIONS:Our findings reveal a regulatory role of Bub3 in DMAP1-mediated DNA methylation upon mitotic stress and provide the relevance of DMAP1 pTyr-246 to mitotic stress resistance during pancreatic cancer treatment.
Project description:Avian reoviruses (ARV) are a group of poultry pathogens that cause runting and stunting syndrome (RSS), a condition otherwise known as "frozen chicken", which are characterized by dramatically delayed growth in broilers. It has been known that p17, a nonstructural protein encoded by ARV, prohibits cellular proliferation by halting the cell cycle at the G2/M phase, the result of which is directly associated with the typical clinical sign of RSS. Nevertheless, the mechanism by which p17 modulates cell-cycle progression remains largely unknown. Here, we screened the interactome of ectopically expressed p17 through a yeast two-hybrid assay and identified Bub3, a cellular mitotic checkpoint protein, as a binding partner of p17. The infection of the Vero cells by ARV downregulated the Bub3 expression, while the knockdown of Bub3 alleviated the p17-modulated cell-cycle arrest during ARV infection. Remarkably, the suppression of Bub3 by RNAi in the Vero cells significantly reduced the viral mRNA and protein abundance, which eventually led to diminished virus replication. Altogether, our findings reveal that ARV p17 impedes host cell proliferation through a Bub3-dependent cell-cycle arrest, which eventually contributes to efficient virus replication. These results also unveil a hitherto unknown therapeutic target for RSS.