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Mapping and characterization of the minimal internal ribosome entry segment in the human c-myc mRNA 5' untranslated region

par Cencig, Sabrina ;Nanbru, Cécile ;Shu-Yun, Le;Gueydan, Cyril ;Huez, Georges ;Kruys, Véronique
Référence Oncogene, 23, page (267-277)
Publication Publié, 2004

Article révisé par les pairs

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Résumé :

The human c-myc proto-oncogene is transcribed from four alternative promoters generating transcripts with 5' untranslated regions of various lengths. These transcripts encode two proteins, c-Myc1 and c-Myc2, from two initiation codons, CUG and AUG, respectively. We and others have previously demonstrated that the region of c-myc transcripts between nucleotides (nt) –363 and –94 upstream from the CUG start codon contained an internal ribosome entry site leading to the cap-independent translation of c-myc open reading frames (ORFs). Here, we mapped a 50-nt sequence (-143 -94), which is sufficient to promote internal translation initiation of c-myc ORFs. Interestingly, this 50-nt element can be further dissected into two segments of 14 nt, each capable of activating internal translation initiation. We also demonstrate that this 50-nt element acts as the ribosome landing site from which the preinitiation ribosomal complex scans the mRNA until the CUG or AUG start codons.