Definition of an efficient synthetic poly(A) site

Genes Dev. 1989 Jul;3(7):1019-25. doi: 10.1101/gad.3.7.1019.


We constructed and analyzed a synthetic poly(A) (SPA) site that was based on the highly efficient poly(A) signal of the rabbit beta-globin gene. By use of the SPA, we demonstrate that the minimum sequences required for efficient polyadenylation are the AATAAA sequence and a GT/T-rich sequence with the correct spacing of 22-23 nucleotides between them. When placed downstream of the poly(A) site of the human alpha 2-globin gene, the SPA is used exclusively. We predict that the SPA, with its more extensive GT/T-rich sequence, is a more efficient poly(A) site than alpha-globin. Also, we compared the use of the SPA when it is placed either in the exon 3 or intron 2 of the rabbit beta-globin gene. When in the exonic position, SPA is used 10-fold more than the regular poly(A) site of rabbit beta-globin. In contrast, when it is in the intronic location, no detectable use of SPA is observed; however, the deletion of the donor site of intron 2 reactivates the intronic positioned SPA. These results indicate that the splicing of intron 2 in the rabbit beta-globin gene occurs ahead of polyadenylation and have important implications for termination of transcription. Polyadenylation, although required for termination of transcription, is not sufficient; therefore, additional termination signals for RNA polymerase II must exist.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Base Sequence
  • DNA / genetics
  • Exons
  • Exonucleases / metabolism
  • Globins / genetics*
  • Humans
  • Introns
  • Molecular Sequence Data
  • Nucleic Acid Hybridization
  • Poly A / genetics*
  • RNA Splicing
  • RNA, Messenger / genetics*
  • Rabbits
  • Restriction Mapping
  • Transcription, Genetic


  • RNA, Messenger
  • Poly A
  • Globins
  • DNA
  • Exonucleases