Stabilization of cyclin E and cdk2 mRNAs at G1/S transition in Rat-1A cells emerging from the G0 state

mRNAs for cyclin E and Cdk2 have a role in the commitment to DNA replication in the cell cycle, and are induced in Rat-1A cells by serum stimulation. Cyclin E and cdk2 genes are transcribed in quiescent cells, but their transcripts rapidly turn over and levels are kept low. The rate of transcription of the cdk2 gene is slightly increased after serum stimulation, while that of cyclin E is fairly constant. At the G1/S transition of serum-stimulated cells, transient stabilization of the two types of mRNAs occurs, an event which may lead to induction of each mRNA. Artificial expression of an immediate-early protein ΔFosB results in proliferation of quiescent Rat-1A cells, and this is accompanied by an efficient induction of cyclin E and cdk2 mRNAs. In ΔFosB-expressing cells, two types of mRNAs are stabilized to the same extent seen in serum-stimulated cells. The expression of cyclin E and cdk2 genes is upregulated by stabilization of their transcripts, at least in part. We propose that ΔFosB may have a role in regulation of progression of the cell cycle in serum-stimulated Rat-1A cells by triggering stabilization of mRNAs for cyclin E and Cdk2.