The p36 isoform of BAG-1 is translated by internal ribosome entry following heat shock

Coldwell, Mark J.; deSchoolmeester, Matthew L.; Fraser, Graham A; Pickering, Becky M.; Packham, Graham; Willis, Anne E.

doi:10.1038/sj.onc.1204547

Cited by 80 publications

(83 citation statements)

References 29 publications

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“…Cellular IRESs are relatively inactive in in vitro reconstituted systems, but can be stimulated by the addition of exogenous proteins. 25,36 In a similar way, IRESs can show marked differences in activity when transfected into different cell lines, and it seems likely that RNA structure alone is not sufficient to confer IRES activity to a cellular 5 0 UTR. A number of ITAFs have been identified (Table 1), which are required for maximal activity of specific IRESs, but to date none has been proposed as a general regulator of IRES function.…”

Section: Analysis Of Mrnas That Remain Polysomally Associated During mentioning

confidence: 99%

Internal ribosome entry segment-mediated translation during apoptosis: the role of IRES-trans-acting factors

et al. 2005

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During apoptosis, there is a reduction in translation initiation caused by caspase cleavage of several of the factors required for the cap-dependent scanning mechanism. Under these circumstances, many proteins that are required for apoptosis are instead translated by the alternative method of internal ribosome entry. This mechanism requires the formation of a complex RNA structural element and in the presence of internal ribosome entry segment (IRES)-trans-acting factors (ITAFs), the ribosome is recruited to the RNA. The interactions of several ITAFs with IRESs have been investigated in detail, and several mechanisms of action have been noted, including acting as chaperones, stabilising and remodelling the RNA structure. Structural remodelling by PTB in particular will be discussed, and how this protein is able to facilitate recruitment of the ribosome to several IRESs by causing previously occluded sites to become more accessible.

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Section: Analysis Of Mrnas That Remain Polysomally Associated During mentioning

confidence: 99%

Internal ribosome entry segment-mediated translation during apoptosis: the role of IRES-trans-acting factors

et al. 2005

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“…BAG-1 expression is highly regulated and since the three major isoforms are generated from a single mRNA transcript (Yang et al, 1998), translational regulation is thought to play a major role in the control of their expression (Yang et al, 1998;Coldwell et al, 2001). The p50 and p46 isoforms are translated by cap-dependent mechanisms whereby a complex of proteins (eukaryotic initiation factor 4F; eIF4F) binds to the 7-methylguanosine cap structure at the 5 0 end of the message and the 40S ribosomal subunit interacts with this complex (Pain, 1996).…”

Section: Introductionmentioning

confidence: 99%

Regulation of BAG-1 IRES-mediated translation following chemotoxic stress

et al. 2007

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There are three major isoforms of BAG-1 in mammalian cells, termed BAG-1L (p50), BAG-1M (p46) and BAG-1S (p36) that function as pro-survival proteins and are associated with tumorigenesis and chemoresistance. Initiation of BAG-1 protein synthesis can occur by both capdependent and cap-independent mechanisms and it has been shown that synthesis of BAG-1S is dependent upon the presence of an internal ribosome entry segment (IRES) in the 5 0 -UTR of BAG-1 mRNA. We have shown previously that BAG-1 IRES-meditated initiation of translation requires two trans-acting factors poly (rC) binding protein 1 (PCBP1) and polypyrimidine tract binding protein (PTB) for function. The former protein allows BAG-1 IRES RNA to attain a structure that permits binding of the ribosome, while the latter protein appears to be involved in ribosome recruitment. Here, we show that the BAG-1 IRES maintains synthesis of BAG-1 protein following exposure of cells to the chemotoxic drug vincristine but not to cisplatin and that this is brought about, in part, by the relocalization of PTB and PCBP1 from the nucleus to the cytoplasm.

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“…BAG-1 exists in human cells as three major isoforms with apparent molecular weights of approximately 36, 46 and 50 kDa (Packham et al, 1997;Takayama et al, 1998;Yang et al, 1998;Brimmell et al, 1999), described here as BAG-1S, BAG-1M and BAG-1L, respectively. BAG-1 isoforms are generated by alternate translation initiation of a single mRNA (Packham et al, 1997;Takayama et al, 1998;Yang et al, 1998;Coldwell et al, 2001) and therefore share a common C-terminus with the larger isoforms having additional N-terminal sequences. The unique N-terminus of BAG-1L contains a nuclear localization sequence and is predominantly located within the nucleus, whereas BAG-1S is predominantly a cytoplasmic protein and BAG-1M partitions between the nucleus and cytoplasm (Packham et al, 1997;Takayama et al, 1998;Yang et al, 1998;Brimmell et al, 1999;Knee et al, 2001).…”

Section: Introductionmentioning

confidence: 99%