Mapping and characterization of the minimal internal ribosome entry segment in the human c-myc mRNA 5' untranslated region.
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.
Cencig
Sabrina
S
Laboratoire de Chimie Biologique, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium.
Nanbru
Cécile
C
Le
Shu-Yun
SY
Gueydan
Cyril
C
Huez
Georges
G
Kruys
Véronique
V
D020121:5' Untranslated Regions / Q000737:chemistry*; D018387:Codon, Initiator; D016259:Genes, myc; D006801:Humans; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger / Q000737:chemistry*; D012270:Ribosomes / Q000378:metabolism*
D020121:5' Untranslated Regions; D018387:Codon, Initiator; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger