A model for the structure and functions of XXXX -responsive elements.

@entity69 @entity68 @entity8282
Most eukaryotic cells express two proteins, whose biosynthetic rates are determined by the intracellular @entity68 status. The genes for both these proteins, ferritin and the @entity69 receptor ( @entity8282 ), are regulated at the post-transcriptional level, but by entirely different mechanisms. Ferritin mRNA levels are not affected by acute changes in @entity68 availability. Ferritin biosynthesis is regulated translationally via a defined element contained within the 5' untranslated region (UTR) of the ferritin mRNA. This element has been highly conserved during evolution and has been termed an @entity68 -responsive element (IRE). In contrast to ferritin, the regulation of @entity8282 biosynthesis is mirrored by equivalent changes in @entity8282 mRNA levels. The genetic information for this regulation is mostly located in the region of the gene encoding the 3' UTR of the @entity8282 mRNA. Five elements that closely resemble the ferritin IRE are contained within the region which is critical for @entity8282 regulation. The IRE is suggested to function by forming a specific stem-loop structure that interacts with a transacting factor in an @entity68 -dependent fashion. We present a model that accommodates the mediation of distinct post-transcriptional regulatory phenomena via IREs.
