Fig 7.

Regulation of RNA surveillance mechanisms in undivided and divided cells. (A) Resting B cells from IgH^frVκ/wt mice were stained with CFSE and then stimulated with LPS for 2 days. A representative dot plot indicates the frequency of divided (CFSE^low) and nondivided (CFSE^high) B cells and the gates used for cell sorting. (B and C) In those sorted cells, NF/F pre-mRNA ratios (B) and relative levels of functional IgH pre-mRNA (C) were obtained as described in the legend to Fig. 4. (D) The NMD efficiency was assessed as described in the legend to Fig. 6 and corresponds to the fold increase in levels of nonproductive Igμ mRNAs upon treatment with CHX. (E) For each sorted population, the splicing efficiency of nonfunctional IgH^frVκ transcripts was calculated for CHX-treated cells by dividing mRNA by pre-mRNA levels, as described in the legend to Fig. 6F. Values obtained for CFSE^high cells were set to 1. (F) Relative levels of nonproductive Igμ mRNAs were calculated for cells treated (+) or not treated (−) with CHX after normalization to GAPDH gene transcripts. Values obtained for CFSE^high cells (without CHX) were set to 1. Results from 7 independent cell sorting experiments are shown. (ns, P > 0.05; ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.001).