Translational initiation competence, 'leaky scanning' and translational reinitiation in areA mRNA of Aspergillus nidulans.

(1) AUG codons that either permit or prevent 'leaky scanning' of mRNA encoding AREA, the transcriptional activator mediating nitrogen metabolite repression in Aspergillus nidulans, have been identified. The consensus context for a strong initiation codon (i.e. one preventing 'leaky scanning') derived from this work is GXX AUG C/UCX. However, AUG codons which do not conform to this consensus are nevertheless able to initiate translation. (2) Translational reinitiation can occur within areA mRNA, although there is a limitation determined by the distance between the chain termination and reinitiation codons and/or the strength of the reinitiation codon. (3) The minimum size of the region of areA mRNA that is competent for initiation of translation has been determined to be 329 nucleotides (nt), and might be at least 975 nt if a 709 bp deletion does not alter it.