Sequential recognition of the pre-mRNA branch point by U2AF65 and a novel spliceosome-associated 28-kDa protein

UMMS Affiliation

Howard Hughes Medical Institute, Program in Molecular Medicine

Publication Date


Document Type



Base Sequence; Cross-Linking Reagents; Molecular Sequence Data; *Nuclear Proteins; *Nucleic Acid Conformation; Protein Binding; RNA Precursors; RNA Splicing; RNA, Messenger; Ribonucleoproteins; Spliceosomes


Life Sciences | Medicine and Health Sciences


Splicing of pre-mRNAs occurs via a lariat intermediate in which an intronic adenosine, embedded within a branch point sequence, forms a 2',5'-phosphodiester bond (RNA branch) with the 5' end of the intron. How the branch point is recognized and activated remains largely unknown. Using site-specific photochemical cross-linking, we have identified two proteins that specifically interact with the branch point during the splicing reaction. U2AF65, an essential splicing factor that binds to the adjacent polypyrimidine tract, crosslinks to the branch point at the earliest stage of spliceosome formation in an ATP-independent manner. A novel 28-kDa protein, which is a constituent of the mature spliceosome, contacts the branch point after the first catalytic step. Our results indicate that the branch point is sequentially recognized by distinct splicing factors in the course of the splicing reaction.


RNA. 1995 Jun;1(4):407-17.

Journal/Book/Conference Title

RNA (New York, N.Y.)

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Link to Article in PubMed

PubMed ID