The Riboprobe® System Vector pSP64 Poly(A) can be used as a standard cloning vector and can also be used for in vitro transcription from the SP6 promoter. The pSP64 Poly (A) Vector can also be used to generate poly(A)+ transcripts in vitro. The vector has a stretch of 30 dA:dT residues inserted between the Sac I and EcoR I sites. Therefore, when foreign DNA is cloned into any polylinker site other than EcoR I (Hind III, Pst I, Sal I, Acc I, Hinc II, Xba I, BamH I, Ava I, Sma I or Sac I), linearization of the recombinant plasmid with EcoR I allows the use of SP6 RNA polymerase in vitro to prepare RNA copies of the inserted sequences that contain a synthetic 3´ “polyA”tail of 30 residues.