Targeting of c-myc and beta-globin coding sequences to cytoskeletal-bound polysomes by c-myc 3' untranslated region.

The influence of the 3′ untranslated region on mRNA localization was investigated by measuring the distribution of myc, beta-globin and hybrid myc-globin mRNAs between free, cytoskeletal-bound and membrane-bound polysomes in cells transfected with either control or chimeric gene constructs. c-myc sequences and beta-globin-coding sequences linked to the myc 3′ untranslated region were present at greatest enrichment in cytoskeletal-bound polysomes. beta-Globin mRNA and myc-coding sequences linked to the beta-globin 3′ untranslated region were recovered largely in the free polysomes. In situ hybridization confirmed that replacement of the c-myc 3′ untranslated region by that of globin caused a relocalization of the mRNA. The results suggest that mRNA localization in differentiated eukaryotic cells depends on a mechanism that involves directional information in the 3′ untranslated region of mRNAs.