Figure 1.  Dynamics of mRNA molecules in the cytoplasm of mammalian cells.  

A. An mRNA transcript that contains the coding sequence of lacZ, 24 MS2 stem–loops and the 3' untranslated region (UTR) of the human growth-hormone gene (hGH) was transiently expressed in COS cells together with the green fluorescent protein (GFP)–MS2 fusion protein. GFP–MS2-tagged RNA particles were followed, and different types of motility were detected in single living cells: directed (Aa), corralled (Ab), static (Ac) and diffusive (Ad). The image in A is a maximum-intensity image projection of 200 time frames. Bar, 10 µm. Panels Aa–Ad are magnified sections of A that show an mRNA track (in green) superimposed on an enlargement from each of the indicated boxed areas. The arrowhead points to a 'static' particle in the vicinity of a 'corralled' particle. Bar, 2 µm.
B. An mRNA transcript that contains the coding sequence of lacZ, 24 MS2 stem–loops and the 3' UTR of SV40 was transiently expressed in COS cells together with the GFP–MS2 protein and analysed as above.

Reproduced with permission from Fusco D, et al, 2003.