Fig. 4: The C-terminal halves of NRBP2 and NRBP1 inhibit L1 retrotransposition and drive full-length NRBP1 to the peripheral region of cells.

a Schematic diagrams of NRBP2 and its mutants. NES: nuclear export signal; NLS: nuclear localization signal; BC box: Elongin BC-binding motif; NRB: nuclear receptor-binding motif. b The NRB and dimerization region are required for NRBP2 to inhibit L1 retrotransposition. Quantification of L1 activity is shown (top). n = 5 biological replicates. Data are mean ± SEM. Two-sided unpaired t-test; no multiple comparison adjustment. One representative Western blot confirming expression of NRBP2 variants is shown (bottom). c The C-terminal half of NRBP2 is necessary and sufficient to inhibit L1. Shown is quantification of L1 activity (top) and one representative Western blot (bottom). n = 2 biological replicates for full-length NRBP2 (no statistical test performed). For NRBP2-N and NRBP2-C, n = 3 biological replicates. Data are mean ± SEM. Two-sided unpaired t-test; no multiple comparison adjustment. d Schematic diagram of NRBP1 and the NRBP1 halves used in this study. LCR: low complexity region; NES: nuclear export signal; NLS: nuclear localization signal; BC box: Elongin BC-binding motif; NRB: nuclear receptor-binding motif. e The C-terminal half of NRBP1 functions oppositely to the full-length NRBP1 and inhibits L1. Shown is the quantification of L1 activity upon expression of the respective NRBP1 variants. For NRBP1, NRBP1-N, and NRBP1-C, the numbers of biological replicates are 6, 3, and 4, respectively. Data are mean ± SEM. Two-sided unpaired t-test; no multiple comparison adjustment. f, g The C-terminal halves of NRBP2 (f, red) and NRBP1 (g, red) promote enrichment of full-length NRBP1 (green) to the peripheral region of HeLa cells. White arrows in (f) indicate NRBP1 localization with NRBP2-N expression; yellow arrows indicate cells with enrichment of NRBP1 to the peripheral region upon NRBP2-C overexpression. Nuclei: blue. Scale bar 10 µm. Shown are representative images of three independent experiments. h Overexpressing NRBP2 and C-terminal half of NRBP1 or NRBP2 reduces endogenous NRBP1 protein level in HeLa cells. Shown is a representative Western blot from three independent experiments. Uncropped blots in Source Data.