iPABP, an inducible poly(A)-binding protein detected in activated human T cells.
The poly(A)-binding protein (PABP) binds to the poly(A) tail present at the 3' ends of most eukaryotic mRNAs. PABP is thought to play a role in both translation and mRNA stability. Here we describe the molecular cloning and characterization of an inducible PABP, iPABP, from a cDNA library prepared from activated T cells. iPABP shows 79% sequence identity to PABP at the amino acid level. The RNA binding domains of iPABP and PABP are nearly identical, while their C termini are more divergent. Like PABP, iPABP is primarily localized to the cytoplasm. iPABP is expressed at low levels in resting normal human T cells; following T-cell activation, however, iPABP mRNA levels are rapidly up-regulated. In contrast, PABP is constitutively expressed in both resting and activated T cells. iPABP mRNA was also expressed at much higher levels than PABP mRNA in heart and skeletal muscle tissue. These data suggest that the regulation of cytoplasmic poly(A)-binding activity is more complex than previously believed. In most tissues, poly(A)-binding activity is likely to be the result of the combined effects of constitutively expressed PABP and iPABP, whose expression is subject to more complex regulation.
Department of Medicine, University of Chicago, Illinois 60637, USA.
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Yang
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Duckett
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Lindsten
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D015723:Gene Library; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D039102:Poly(A)-Binding Proteins; D016133:Polymerase Chain Reaction; D011131:Polyribonucleotides / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
D017931:DNA Primers; D039102:Poly(A)-Binding Proteins; D011131:Polyribonucleotides; D012333:RNA, Messenger; D016601:RNA-Binding Proteins