Fig 2: Pp1c expression in border cells and specificity of NiPp1 inhibition of Pp1c activity.(A–F) Stage 9 and 10 egg chambers showing the endogenous patterns of Pp1c subunits (green) in border cells (arrowheads), follicle cells, and the germline nurse cells and oocyte. DAPI (blue) labels nuclei. Insets, zoomed-in detail of border cells from the same egg chambers. (A–C) Pp1a-96A (green) expression, visualized by a GFP-tagged fly-TransgeneOme (fTRG) line. (D–F) Flw expression (green), visualized by a YFP-protein trap in the endogenous flw genetic locus. (G, H) Overexpression of Pp1c genes rescues the migration (G) and cluster cohesion (H) defects of NiPp1-expressing border cells. (G) Quantification of the migration distance at stage 10 for border cells in NiPp1-expressing egg chambers versus rescue by overexpression of the indicated Pp1c genes, shown as complete (green) and incomplete (red) border cell migration (see Figure 1I for egg chamber schematic). (H) Quantification of cluster cohesion at stage 10, shown as the percentage of border cells found as a single unit (one part) or split into multiple parts (two parts, three parts,>3 parts) in NiPp1-expressing egg chambers versus rescue by overexpression of the indicated Pp1c genes. (G, H) Error bars represent SEM in three experiments, each trial assayed n = 44 egg chambers (total n = 148 per genotype). *p<0.05, **p<0.01; ***p<0.001; ****p<0.0001, unpaired two-tailed t test. All genotypes are listed in Table 2.

Fig 3: Pp1, through myosin phosphatase, promotes contractility of the cluster.(A–B’’) Pp1 restricts Myo-II activation to the cluster periphery. Representative images showing p-Sqh localization (white in A, B; red in A’’, (B’’) and membrane GFP (PLCd-PH-EGFP; green in A’, (A’’, B’, B’’) in control (A–A’’) and NiPp1 overexpressing (B–B’’) border cells; DAPI labels nuclei (blue in A’’, (B’’). There is an increase in p-Sqh levels (arrowheads) at the interface between border cells when NiPp1 is overexpressed. (C) Quantification of the mean pixel intensity of p-Sqh as a ratio of BC:NC/BC:BC. BC:NC stands for border cell-nurse cell interfaces, while BC:BC stands for border cell-border cell interfaces. N = 15 for control and n = 11 for NiPp1 overexpression. (D–H) Knocking down Mbs disrupts border cell migration and cluster cohesion. (D–F) Stage 10 control (D) and Mbs RNAi (E,F) egg chambers stained for SN to label border cells (green), phalloidin to label F-actin (red) and DAPI to label nuclei (blue). (G) Quantification of border cell cluster migration for matched control and Mbs-RNAi, shown as the percentage that did not complete (red), or completed (green) their migration to the oocyte (see Figure 1I for egg chamber schematic). (H) Quantification of cluster cohesion at stage 10, shown as the percentage of border cells found as a single unit (one part) or split into multiple parts (two parts, three parts,>3 parts) in control versus Mbs-RNAi border cells. (G, H) Each trial assayed n = 61 egg chambers (total n = 220 per genotype). **p<0.01; ****p<0.0001; unpaired two-tailed t test. All genotypes are listed in Table 2.

Fig 4: NIPP1 mRNA expression is upregulated in several cancers. The NIPP1 mRNA expression levels in normal solid tissue and primary tumors of each cancer type dataset in TCGA were obtained using UCSC Xena. The fold-change was calculated using the median. Data for the top 5 upregulated cancer types are shown. In the box plot, the central line reflects the median, while the borders of the boxes show the interquartile range of the plotted data. The whiskers extend to 1.5-fold the interquartile range, and outliers are not shown

Fig 5: NIPP1 is required for the transcription of specific gene functions of E2F target genes. A, Parental and corresponding NIPP1-depleted HeLa cell lines by CRISPR/Cas9 were analyzed by immunoblotting with the indicated antibodies. B, Real-time PCR analysis of CDK1, CCNB1, and CCND1 expression in control and NIPP1-depleted HeLa cells. Data are provided as the mean ± SEM of 3 independent experiments. The results were considered statistically significant at *P < .05 and **P < .01. C, Control and NIPP1-depleted HeLa cells were cultured and collected, and the cell numbers were counted. Data are provided as the mean ± SE of the mean (SEM) of 3 independent experiments. The results were considered statistically significant at *P < .05 and **P < .01. D, Cell cycle distributions of control and NIPP1-depleted HeLa cells were verified by FACS analysis. Each cells were stained with EdU and PI. Fractions of cells in each phase of the cell cycle were quantified. Data are provided as the mean ±SEM of 3 independent experiments. The results were considered statistically significant at *P < .05 and **P < .01. E, F, The enrichment plot of HALLMARK_E2F_TARGETS (E) and HALLMARK_MYC_TARGETS_V1 (F) in NIPP1-KO mouse testis compared with NIPP1-WT was generated using GSEA software. NES: normalized enrichment score; FDR: false discovery rate. Four biological replicates were analyzed. G, The enrichment plot of E2F1_BINGING_OVER_750 in NIPP1-KO mouse testis compared with NIPP1-WT was generated using GSEA software. E2F1 target gene set containing E2F1 binding score higher than 750 in E2F target genes (n = 49). 32 NES: normalized enrichment score; FDR: false discovery rate. Four biological replicates were analyzed. H, Pearson's correlation coefficient between NIPP1 and the E2F1 target genes and heat map in TCGA Pan-Cancer dataset (n = 11 060) were calculated using UCSC Xena. I, Violin plot of correlation coefficient between NIPP1 and E2F target (n = 123) or non-E2F target genes (n = 20 188) in TCGA Pan-Cancer dataset (n = 11 060) was calculated using UCSC Xena. The results were considered statistically significant at *P < .05 and **P < .01 [Correction added on 14 May 2021, after first online publication: Figures 2A and C have been corrected.]