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. 2005 Apr 15;19(8):933–941. doi: 10.1101/gad.333205

Figure 1.

Figure 1.

Stress-induced activation of JNK inhibits Pol I transcription. (A) Cellular stress induces JNK activity and impairs rRNA synthesis. RNA from HEK293T cells that were mock-treated or treated with H2O2 (200 μM, 60 min), BSO (1 mM, 16 h), anisomycin (10 μM, 60 min), SB203580 (2 μM, 20 min), or SP600125 (5 μM, 30 min) followed by anisomycin (10 μM, 60 min) was analyzed on Northern blots for 45S pre-rRNA (upper panel) and JNK2 activity and levels (lower two panels). To measure JNK2 activity, HEK293T cells were transfected with pcDNA3.1HA-JNK2 and subjected to the indicated stress stimuli. HA-JNK2 was immunopurified from 2 × 106 cells and tested for kinase activity using purified GST-tagged c-Jun (amino acids 1-166). Western blots of cellular lysates were probed using antibodies against overexpressed HA-JNK2. A bar diagram shows quantification of levels of pre-rRNA (normalized to actin-mRNA signals) and phospho-c-Jun (normalized to HA-JNK western blot units). Error bars denote the standard deviation derived from three independent experiments. (B) Stress does not impair pre-rRNA synthesis in Jnk2 single and Jnk1,2 double-knockout fibroblasts. 45S pre-rRNA was monitored on Northern blots using 3 μg RNA from parental and Jnk1,2-/- MEFs (top panel) or immortalized Jnk1-/- and Jnk2-/- NIH3T3 cells (bottom panel) treated with H2O2 (200 μM, 60 min), BSO (1 mM, 16 h), or anisomycin (10 μM, 60 min). In the bottom panel, the filter was reprobed to detect actin-mRNA.