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. 2021 Jul 2;12:4090. doi: 10.1038/s41467-021-24373-5

Fig. 6. SS18 regulates PST through mediating the assembly balance among BAF ncBAF and PBAF.

Fig. 6

a Representative images of immunofluorescence for endogenous BAF specific subunit DPF2 in SS18KO mESCs infected with lentiviral SS18-EGFP. The graph on the right shows pixel intensity across five condensates of SS18-EGFP (green) and DPF2 (red). Scale bars, 3 μm. SS18-EGFP, laser intensity 2.5%, detector gain 500 V. DPF2 immunofluorescence, laser intensity 3.5%, detector gain 750 V. Both SS18-EGFP and DPF2 immunofluorescence were processed by background subtraction. Three independent experiments. b Representative images of the immunofluorescence for endogenous PBAF specific subunit BRD7 in SS18KO mESCs with exogenous SS18-EGFP. The graph on the right shows pixel intensity across five condensates of SS18-EGFP and BRD7 (red). Note no co-localization between SS18 and BRD7. Scale bars, 3 μm. SS18-EGFP, laser intensity 2.5%, detector gain 500 V. BRD7 immunofluorescence, laser intensity 3.5%, detector gain 750 V. Both SS18-EGFP and BRD7 immunofluorescence were processed by background subtraction. Three independent experiments. c The histogram shows the relative precipitated abundance of indicated proteins to BRG1 as quantified by normalized LFQ intensity from IP-MS experiments by anti-BRG1 antibody performed on WT and SS18KO mESCs. IP-MS experiments were performed in triplicates and a two-sample t test was applied. Data are mean ± s.d., two-sided, unpaired t test; n = 3 independent experiments, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. d The expression levels of Nanog by Jun-FlagTetON mESCs at 8 h during PST with knocking down of indicated components of BAF ncBAF or PBAF. G1 + G1l, knockdown Gltscr1 and Gltscr1l jointly. Data are mean ± s.d., two -sided, unpaired t test; n = 3 independent experiments, **p < 0.01, ***p < 0.001, ****p < 0.0001. e A working model for SS18-mediated PST. SS18 functions by interacting with BAF or ncBAF subunits through its N-terminal 70aa, and forming condensates through a tyrosine-rich IDR. Meanwhile, the full length of SS18, co-localizing with BAF-specific component and isolating PBAF-specific one, can promote the BAF complex assembly and impair that of PBAF. In WT cells, BAF ncBAF and PBAF reach a balance. In SS18KO cells, the balance shifts towards PBAF to cause a delay in PST.