title: CRD-BP shields c-myc and MDR-1 RNA from endonucleolytic attack by a mammalian endoribonuclease.
abstract: The c-myc mRNA coding region determinant-binding protein (CRD-BP) has high affinity for the coding region determinant (CRD) of c-myc mRNA. Such affinity is believed to protect c-myc CRD from endonucleolytic attack. We have recently purified a mammalian endoribonuclease which can cleave within the c-myc CRD in vitro. The availability of this purified endonuclease has made it possible to directly test the interaction between CRD-BP and the endonuclease in regulating c-myc CRD RNA cleavage. In this study, we have identified the coding region of MDR-1 RNA as a new target for CRD-BP. CRD-BP has the same affinity for c-myc CRD nts 1705-1886 and MDR-1 RNA nts 746-962 with K(d) of 500 nM. The concentration-dependent affinity of CRD-BP to these transcripts correlated with the concentration-dependent blocking of endonuclease-mediated cleavage by CRD-BP. In contrast, three other recombinant proteins tested which had no affinity for c-myc CRD did not block endonuclease-mediated cleavage. Finally, we have identified RNA sequences required for CRD-BP binding. These results provide the first direct evidence that CRD-BP can indeed protect c-myc CRD cleavage initiated by an endoribonuclease, and the framework for further investigation into the interactions between CRD-BP, c-myc mRNA, MDR-1 mRNA and the endoribonuclease in cells.
authors.affiliation: Chemistry Program, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada.
authors.forename: Dan
authors.initials: D
authors.lastname: Sparanese
authors.forename: Chow H
authors.initials: CH
authors.lastname: Lee
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004722:Endoribonucleases / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C519161:CRD-BP protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D004722:Endoribonucleases