Component of the TRAMP (TRF4) and TRAMP5 complexes which have a poly(A) RNA polymerase activity and are involved in a post-transcriptional quality control mechanism limiting inappropriate expression of genetic information. Polyadenylation is required for the degradative activity of the exosome on several of its nuclear RNA substrates like cryptic transcripts generated by RNA polymerase II and III, or hypomethylated pre-tRNAi-Met. Both complexes polyadenylate RNA processing and degradation intermediates of snRNAs, snoRNAs and mRNAs that accumulate in strains lacking a functional exosome. Component of the TRAMP complex (also called TRF4 complex) composed of at least mtr4, pap2/trf4 and air1. Component of the TRAMP5 complex composed of at least air1, mtr4 and trf5. Interacts with cid14. Belongs to the AIR1 family.