title: Human PABP binds AU-rich RNA via RNA-binding domains 3 and 4.
abstract: Poly(A) binding protein (PABP) binds mRNA poly(A) tails and affects mRNA stability and translation. We show here that there is little free PABP in NIH3T3 cells, with the vast majority complexed with RNA. We found that PABP in NIH3T3 cytoplasmic lysates and recombinant human PABP can bind to AU-rich RNA with high affinity. Human PABP bound an AU-rich RNA with Kd in the nm range, which was only sixfold weaker than the affinity for oligo(A) RNA. Truncated PABP containing RNA recognition motif domains 3 and 4 retained binding to both AU-rich and oligo(A) RNA, whereas a truncated PABP containing RNA recognition motif domains 1 and 2 was highly selective for oligo(A) RNA. The inducible PABP, iPABP, was found to be even less discriminating than PABP in RNA binding, with affinities for AU-rich and oligo(A) RNAs differing by only twofold. These data suggest that iPABP and PABP may in some situations interact with other RNA regions in addition to the poly(A) tail.
authors.affiliation: Division of Human Immunology and Hanson Institute, Institute of Medical and Veterinary Science, Adelaide, Australia.
authors.forename: Rosemary T
authors.initials: RT
authors.lastname: Sladic
authors.forename: Cathy A
authors.initials: CA
authors.lastname: Lagnado
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bagley
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Goodall
mesh_terms: D020856:AT Rich Sequence / Q000502:physiology*; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D003593:Cytoplasm; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D011061:Poly A / Q000235:genetics / Q000378:metabolism; D039122:Poly(A)-Binding Protein I / Q000378:metabolism*; D039102:Poly(A)-Binding Proteins / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001798:Blood Proteins; C104581:PABPC4 protein, human; D039122:Poly(A)-Binding Protein I; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D011061:Poly A