PolyA-binding protein (PABP) is a ubiquitous RNA binding protein that contains 4 RNA recognition motifs and a proline-rich C-terminal domain responsible for protein-protein interaction. It is an important regulator of mRNA stability and translation. PABPC4 or inducible PABP (iPABP), which share 79% sequence identity with PABP1, were cloned using activated human T cells. Like PABP1, iPABP was primarily localized to the cytoplasm and possessed RNA binding properties remarkably similar to those of PABP. iPABP was expressed at low levels in resting T cells; however, after T cell activation, iPABP mRNA levels increased by approximately 5 fold. The presence of iPABP might be essential for regulating the stability of unstable mRNA species in activated T cells.