Abstract

lnterleukin-1β (11-1β), a key cytokine in the acute phase response, elevates hepatic expression of both the heavy (H) and light (L) ferritin subunits without influencing the steady-state levels of either ferritin transcript. Transfection experiments with human hepatoma cells reveal that sequences within the 5′ untranslated region (5′UTR) of H-ferritin mRNA confer translational regulation to chimaeric chloramphenicol acetyl transferase (CAT) mRNAs in response to 11-1β in the absence of marked changes in CAT mRNA levels. 11-1β dependent translational enhancement is mediated by a distinct G + C rich RNA sequence within 70 nucleotides (nt) of the start codon. The upstream Iron Responsive Element RNA stemloop does not confer increased expression to CAT mRNA in II-1β stimulated hepatoma transfectants. A 38 nucleotide consensus sequence within the 5′UTRs of the mRNAs encoding the hepatic acute phase proteins α 1 -antitrypsin (α 1 ;AT), α 1 -acid glycoprotein (AGP) and haptoglobin (Dente et al ., 1985) is similar to sequences in the G + C rich Hferritin mRNA translational regulatory element. Deletion of three nucleotides from this region of the 61 nt G + C rich element in the H-ferritin mRNA 5′ leader eliminates II-1β translational enhancement of the CAT reporter transcripts.

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