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Bimolecular Exon Ligation by the Human Spliceosome

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Science  13 Jun 1997:
Vol. 276, Issue 5319, pp. 1712-1716
DOI: 10.1126/science.276.5319.1712

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Abstract

Intron excision is an essential step in eukaryotic gene expression, but the molecular mechanisms by which the spliceosome accurately identifies splice sites in nuclear precursors to messenger RNAs (pre-mRNAs) are not well understood. A bimolecular assay for the second step of splicing has now revealed that exon ligation by the human spliceosome does not require covalent attachment of a 3′ splice site to the branch site. Furthermore, accurate definition of the 3′ splice site in this system is independent of either a covalently attached polypyrimidine tract or specific 3′ exon sequences. Rather, in this system 3′ splice site selection apparently occurs with a 5′ → 3′ directionality.

  • * To whom correspondence should be addressed. E-mail: mmoore{at}binah.cc.brandeis.edu

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