C-Myc 5′ untranslated region contains an internal ribosome entry segment

Differential expression of Myc1 and Myc2 isoforms in cells transformed by eIF4E: evidence for internal ribosome repositioning in the human c-myc 5′UTR

“…Therefore, we have focused our investigation primarily on P1-initiated transcripts. Recent work with the human cmyc 5'UTR also suggests the existence of an IRES (Internal Ribosome Entry Site), as assayed with a bicistronic reporters (Nanbru et al, 1997;Stonely et al, 1998). These studies, however, do not rule out other possibilities and do not address the problem of translation initiation at the upstream CUG codon (Myc1).…”

A mutation in the c-myc-IRES leads to enhanced internal ribosome entry in multiple myeloma: A novel mechanism of oncogene de-regulation

“…The latter is mediated by structured regions of RNA termed internal ribosome entry segments (IRES), and these have the ability to direct ribosome binding some considerable distance (up to 1000 nts) from the 5' end of the message. IRESs were originally discovered in picornaviral mRNAs, but have now been identi®ed in a number of eukaryotic mRNAs, the protein products of which are involved in the control of cell growth including, FGF-2 (Vagner et al, 1995), VEGF (Miller et al, 1998;Stein et al, 1998), PDGF (Bernstein et al, 1997) and c-myc (Nanbru et al, 1997;Stoneley et al, 1998) and cell death Holcik et al, 1999). In the case of c-myc we have shown that initiation of protein synthesis can occur by two distinct mechanisms; cap-dependent scanning and IRES mediated .…”

“…The 5' untranslated region of the proto-oncogene c-myc contains an internal ribosome entry segment (IRES) (Nanbru et al, 1997;Stoneley et al, 1998) and thus cmyc protein synthesis can be initiated by a capindependent as well as a cap-dependent mechanism . In cell lines derived from patients with multiple myeloma (MM) there is aberrant translational regulation of c-myc and this correlates with a C-T mutation in the c-myc-IRES .…”

“…This vector contains the Renilla and Fire¯y luciferase genes upstream and downstream respectively of a spacer region (Figure 2a) . We have shown previously that insertion of the c-myc IRES into this intercistronic region results in a 50 ± 100-fold increase in the activity of the ®re¯y luciferase by internal ribosome entry (Stoneley et al, 1998). The WT and MT versions of this dicistronic plasmid (pRMF and pRMFmt) were then transfected into a number of cell types.…”

“…Cells were grown in RPMI (GM2132, GM03201) or DMEM (HeLa, GM637) containing 10% foetal calf serum in a humidi®ed atmosphere containing 5% CO 2 . Cells were transfected with pRMF (that contains the wild type IRES; Stoneley et al, 1998) or pRMFmt and the bgalactosidase encoding construct pcDNA3. 1/HisB/Lacz (Invitrogen) using either calcium phosphate DNA co-precipitation (Auscbel, 1987) or by electroporation (GM2132 and GM03201) using a BioRad Gene pulser.…”