Fig. 6.

FOXP1 represses germinal center B-cell gene and MHC Class II expression in favor of partial plasma cell differentiation. (A) Heatmap of GCB and plasmablast (PB)/plasma cell (PC)-related genes after FOXP1 KD via shRNAs at indicated times in TMD8 and HBL1 ABC lines. GCB genes (left, green) are repressed by FOXP1, whereas PB/PC genes (left, blue) are activated, with the exception of PRDM1, encoding BLIMP-1, the master regulator of PC differentiation. Typically high GCB expression of MHC class II structural (HLA) and master regulator CIITA (red) are repressed. (B) FOXP1 is recruited to regulatory loci of GCB and PB/PC-related genes. ChIP-seq peaks from seven DLBCL cell lines are shown as read density tracks. In general, many loci had aligned peaks across all seven lines, whereas others had aligned peaks only in ABC lines, indicating different binding patterns between the DLBCL types. (C) MHC class II expression is restored after FOXP1 loss. Pan-MHC class II expression as measured by flow cytometry was markedly increased 4 d after FOXP1 KD in ABC cell line HBL1 but not in TMD8.