title: Evidence that a specific interaction between an 18-base cis-element in the 5'-untranslated region of human folate receptor-alpha mRNA and a 46-kDa cytosolic trans-factor is critical for translation.
abstract: Folate receptors (FR) are inversely regulated by the extracellular folate concentration at the translational level in cervical carcinoma cells. Accordingly, the potential for interaction of cis-elements in FR-alpha mRNA and trans-factors in these cells was determined. Gel-shift assays identified two signals that were specifically derived from the interaction of cytosolic proteins with the 5'-untranslated region of FR-alpha mRNA. RNase T1 mapping revealed that the RNA sequences interacting with these proteins were located between nucleotides -133 to -116 (18-bases) and -158 to -116 (43-bases), upstream of the translation start site. However, selective RNase H cleavage indicated that the 18-base RNA sequence was the cis-element. The RNA-protein interaction was competed by poly(C), but not by poly(U), homopolymers. UV cross-linking and Northwestern blot analysis confirmed that the trans-factors were 46-kDa proteins. An 18-base antisense oligodeoxynucleotide complementary to the cis-element specifically quenched the RNA-protein interaction and also completely inhibited translation of FR-alpha mRNA without changing its stability. Thus, the interaction of the 18-base cis-element and the 46-kDa trans-factors likely have an important role in translational regulation of FR. In addition, because the 46-kDa proteins were widely distributed in cells expressing little to no FR-alpha, these species probably have additional functions that are unrelated to translation of FR.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
authors.forename: X L
authors.initials: XL
authors.lastname: Sun
authors.forename: A C
authors.initials: AC
authors.lastname: Antony
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D005260:Female; D058973:Folate Receptors, GPI-Anchored; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D016914:Ribonuclease H; D006163:Ribonuclease T1; D002583:Uterine Cervical Neoplasms / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D016914:Ribonuclease H; D006163:Ribonuclease T1