Figure 1.

MS2 system for fluorescent labeling of mRNAs in living cells. (A) Schematic of a reporter mRNA that contains multiple copies of the MS2 stem-loop (boxed) that bind to the MS2 coat protein fused to GFP (arrows). The binding of many MCP-GFP molecules to a single transcript allows the RNA to be observed in living cells. (B) Transcription in the nucleus detected by binding of MCP-GFP to nascent mRNAs at the transcription site. (From Darzacq et al. 2007; reprinted, with permission, from the author.) (C) Tracking of single mRNAs (trajectory shown as line) in the nucleoplasm. (From Shav-tal et al. 2004; reprinted, with permission, from The American Association for the Advancement of Science © 2004.) (D) Single mRNAs detected in the cytoplasm. (From Fusco et al. 2003; reprinted, with permission, from Elsevier © 2003.)