Poly(A) polymerase is
Polyadenylate polymerase is classified as template-independent terminal nucleotidyltransferase, lacking ability to read DNA or RNA template for base selection. Instead specificity arises from intrinsic preference for ATP binding pocket and interactions with CPSF and PABPN1. Therefore polyadenine sequence is not encoded in genome but added post-transcriptionally forming uniform adenine homopolymer essential for stability. This contrasts with DNA polymerases, RNA polymerases that are template dependent. Other template independent polymerases include CCA-adding enzyme for transfer RNA and terminal deoxynucleotidyl transferase TdT in immunoglobulin gene rearrangement adding N-nucleotides.
Ref: Berg et al., Biochemistry, 9th ed., Chapter 28: Poly(A) polymerase template independent; Lodish 9th ed., Terminal nucleotidyltransferase family