The 5′‐untranslated region of the human muscle acylphosphatase mRNA has an inhibitory effect on protein expression

Abstract

The cDNA of the human muscle type acylphosphatase was isolated and characterized. The mRNA presents a very long 5'-untranslated region, covering the first half of the molecule: 175 bases of this part were cloned and prediction of the possible secondary structure showed that a very stable stem-loop structure could be formed in that region. Moreover, an additional AUG triplet was found upstream of the start codon of the protein, defining an open reading frame of 60 codons which overlapped that of acylphosphatase. The possible regulatory effect on translation of this part of the mRNA molecule was studied by means of transient transfection experiments: a 10-fold decrease in the expression of a reporter protein and a dramatic decrease in the corresponding mRNA was observed, due to the presence of the 5'-untranslated region of acylphosphatase mRNA. Mutagenesis of the upstream AUG triplet eliminated mRNA instability, leading to the hypothesis that the product of the upstream open reading frame could play a role in this mechanism.

Drosophila melanogaster acylphosphatase: A common ancestor for acylphosphatase isoenzymes of vertebrate species

“…Moreover, it can be observed that nearly half of the single mRNA transcript coding for AcPDro is unusually covered by the 5'-UTR. A very similar situation has been found for the human MT-AcP mRNA where it was also evidenced that the 5'-UTR plays a role in the stability of the mRNA molecule [26].…”

Acylphosphatase Is a Strong Apoptosis Inducer in HeLa Cell Line

“…Surprisingly, the N41Q-AcP mutant, a protein that has lost most of its in vitro acylphosphatase activity on benzoyl-phosphate [18] and ATP [23], behaves exactly as the wild-type enzyme for what cell survival is concerned, thus suggesting that the well characterized in vitro acylphosphatase activity of this protein is not necessary for AcP-induced cell death. The results that we have exposed in this work are very interesting in the light of an important observation of Fiaschi et al [13] on the regulation of AcP expression mediated by the 5Ј-UTR of its mRNA. The primary target for translational control is at the initiation step, and control of translational initiation on individual mRNA is determined primarily by the structural properties of the mRNA, particularly the 5Ј-UTR [24].…”

“…The most important 5Ј-UTR features that control mRNA translation are its secondary structures, the presence of additional initiation AUG codons and of an upstream open reading frame. Fiaschi et al [13] have found that the 5Ј-UTR of AcP has an inhibitory effect on protein expression because possess both an upstream AUG and a very stable stem-loop structure. Interestingly, only less than 10% of the vertebrate mRNAs contains initiation codons upstream the major open reading frame [25].…”

“…In fact, increase of both isoforms can be observed in the K562 erythroid cell line after induction of differentiation [12]. In a recent paper, Fiaschi et al [13] have shown that the 5Ј-untranslated region (5Ј-UTR) of human AcP muscle isoform has an inhibitory effect on AcP expression. In fact, the 5Ј-UTR of the AcP mRNA presents an AUG triplet upstream the protein start codon and a very stable stem-loop structure.…”

“…In fact, the 5Ј-UTR of the AcP mRNA presents an AUG triplet upstream the protein start codon and a very stable stem-loop structure. Both these features contribute to the inhibition of mRNA translation [13]. Modulation of translation rate has long been recognized as a mechanism for controlling global synthetic activity of the cell.…”