Localisation of a reporter transcript by the c-myc 3 '-UTR is linked to translation

The 3'-untranslated region of c-myc mRNA contains a perinuclear localisatio n signal which is sufficient to target beta-globin coding sequences. The li nk between perinuclear RNA localisation and translation has been investigat ed using cells transfected with chimeric gene constructs in which globin re porter sequences were linked to the c-myc 3'-untranslated region and the ir on-responsive element from ferritin mRNA. Iron supplementation of the mediu m promoted translation of the chimeric mRNA as assessed by its presence in polysomes; in situ hybridisation showed that the mRNA was localised around the nucleus. Treatment with the iron chelator desferrioxamine for 16 h prev ented both translation and mRNA localisation. In controls where the express ed mRNA lacked the iron-responsive element desferrioxamine had no effect up on localisation. In contrast, arrest of on-going global translation by puro mycin treatment had no effect on mRNA localisation. The data suggest that i f initiation of translation of a mRNA containing the c-myc localisation sig nal is prevented in some way then localisation does not occur, whereas once the mRNA has been localised further translation is not required to maintai n mRNA localisation.