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. 2009 Sep 1;122(19):3481–3491. doi: 10.1242/jcs.048678

Fig. 1.

Fig. 1.

Expression of p8 during the cell cycle. (A) Northern blot analysis of total RNA isolated from growing myoblasts (Mb) and arrested myoblasts (G0) of the p8 gene-trap clone gtQ39 (top panels) and parental C2C12 cells (bottom panels). In gtQ39 cells, the β-galactosidase (βgal) probe detects a gene-trap fusion transcript (exon 1 of p8 fused to the βgal-coding sequences) that is upregulated ∼fivefold in G0. Expression of endogenous p8 RNA in parental C2C12 cells (detected using a p8-specific probe) is also induced >fivefold by arrest. 28S rRNA and L7 RNA serve as loading controls. (B) p8 expression is further activated during the G0-G1 transition, reaching 20-fold induction in mid-G1. G0, northern blot analysis of arrested myoblasts 48 hours after induction of arrest; R2-24, G0-synchronized cells reactivated into the cell cycle for the indicated number of hours. Histone mRNA reports the proportion of cells in S phase. (C) MyoD expression during a timecourse of reversible arrest as in B. Expression of the MyoD transcript is induced in G1, later than p8 expression.