Bag-1 internal ribosome entry segment activity is promoted by structural changes mediated by poly(rC) binding protein 1 and recruitment of polypyrimidine tract binding protein 1.
We have shown previously that an internal ribosome entry segment (IRES) directs the synthesis of the p36 isoform of Bag-1 and that polypyrimidine tract binding protein 1 (PTB-1) and poly(rC) binding protein 1 (PCBP1) stimulate IRES-mediated translation initiation in vitro and in vivo. Here, a secondary structural model of the Bag-1 IRES has been derived by using chemical and enzymatic probing data as constraints on the RNA folding algorithm Mfold. The ribosome entry window has been identified within this structural model and is located in a region in which many residues are involved in base-pairing interactions. The interactions of PTB-1 and PCBP1 with their cognate binding sites on the IRES disrupt many of the RNA-RNA interactions, and this creates a largely unstructured region of approximately 40 nucleotides that could permit ribosome binding. Mutational analysis of the PTB-1 and PCBP1 binding sites suggests that PCBP1 acts as an RNA chaperone to open the RNA in the vicinity of the ribosome entry window while PTB-1 is probably an essential part of the preinitiation complex.
Pickering
Becky M
BM
Department of Biochemistry, University of Leicester, LE1 7RH, United Kingdom.
Mitchell
Sally A
SA
Spriggs
Keith A
KA
Stoneley
Mark
M
Willis
Anne E
AE
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D038941:Polypyrimidine Tract-Binding Protein / Q000031:analogs & derivatives / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012270:Ribosomes / Q000378:metabolism*; D014157:Transcription Factors
C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C094604:PCBP1 protein, human; C450006:PTBP1 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D038941:Polypyrimidine Tract-Binding Protein