Binds the poly(A) tail of mRNA. Appears to be an important mediator of the multiple roles of the poly(A) tail in mRNA biogenesis, stability and translation (By similarity). During infection with potyvirus TuMV, acts as a potential integral component of the viral replicase complex that could play an important role in the regulation of potyviral RNA-dependent RNA polymerase (RdRp) (By similarity). Interacts with ERD15/CID1. Interacts with Turnip mosaic virus (TuMV) VPg-Pro. By potyvirus TuMV infection. Pab2 and pab4 double mutants show significant growth and development defects and more resistance to Turnip mosaic virus (TuMV). A.thaliana contains 8 PABP genes. Belongs to the polyadenylate-binding protein type-1 family.