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.
Yang
H
H
Department of Medicine, University of Chicago, Illinois 60637, USA.
Duckett
C S
CS
Lindsten
T
T
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