Notch signaling controls cell fate decisions in many contexts during development and adult stem cell homeostasis and, when dysregulated, leads to carcinogenesis. The central transcription factor RBPJ assembles the Notch coactivator complex in the presence of Notch signaling, and represses Notch target gene expression in its absence. We identified L3MBTL2 and additional members of the non-canonical polycomb repressive PRC1.6 complex in DNA-bound RBPJ associated complexes and demonstrate that L3MBTL2 directly interacts with RBPJ. Depletion of RBPJ does not affect occupancy of PRC1.6 components at Notch target genes. Conversely, absence of L3MBTL2 reduces RBPJ occupancy at enhancers of Notch target genes. Since L3MBTL2 and additional members of the PRC1.6 are known to be SUMOylated, we investigated whether RBPJ uses SUMO-moieties as contact points. Indeed, we found that RBPJ binds to SUMO2/3 and that this interaction depends on a defined SUMO-interaction motif. Furthermore, we show that pharmacological inhibition of SUMOylation reduces RBPJ occupancy at Notch target genes. We propose that the PRC1.6 complex and its conjugated SUMO-modifications provide a favorable environment for binding of RBPJ to Notch target genes.

中文翻译：

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SUMO化非规范多梳PRC1.6复合物作为转录因子RBPJ募集的先决条件

Notch 信号在发育和成体干细胞稳态期间的许多情况下控制细胞命运决定，当失调时，会导致癌变。中心转录因子 RBPJ 在存在 Notch 信号的情况下组装 Notch 共激活因子复合物，并在其不存在时抑制 Notch 靶基因的表达。我们在 DNA 结合的 RBPJ 相关复合物中鉴定了 L3MBTL2 和非规范多梳抑制性 PRC1.6 复合物的其他成员，并证明 L3MBTL2 直接与 RBPJ 相互作用。RBPJ 的消耗不影响在 Notch 靶基因处PRC1.6 成分的占有率。相反，L3MBTL2 的缺失会降低 RBPJ 在 Notch 靶基因增强子上的占有率。由于已知 L3MBTL2 和 PRC1.6 的其他成员是 SUMOylated，我们调查了 RBPJ 是否使用 SUMO 部分作为接触点。