Figure 5.

SRF activation does not require CRM1. (A) Leptomycin B does not inhibit serum activation of SRF. NIH3T3 cells transfected with 3D.ALuc were serum starved and restimulated in the presence or absence of 5 nM leptomycin B (LMB). (B) Leptomycin B does not inhibit SRF transcriptional shutdown after serum stimulation. Total cell RNA was prepared from 3D.A-fosHA cells, which contain a stably integrated SRF reporter gene, at various times after serum stimulation after pretreatment with 10 nM LMB as indicated. Transcripts of the 3D.A-fosHA reporter, endogenous c-fos, and control GAPDH were analyzed by RNase protection. An identical result was obtained using 50 nM LMB. (C) Quantification of RNase protection assay. The experiment in B was analyzed using the PhosphorImager. Charts show reporter and c-fos transcript levels relative to GAPDH control.