Human step II splicing factor hSlu7 functions in restructuring the spliceosome between the catalytic steps of splicing (original) (raw)

1. Katrin Chua and
2. Robin Reed
3. Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115 USA

Abstract

The spliceosome catalyzes pre-mRNA splicing in two steps. After catalytic step I, a major remodeling of the spliceosome occurs to establish the active site for step II. Here, we report the isolation of a cDNA encoding hSlu7, the human homolog of the yeast second step splicing factor Slu7. We show that hSlu7 associates with the spliceosome late in the splicing pathway, but at a stage prior to recognition of the 3′ splice site for step II. In the absence of hSlu7, splicing is stalled between the catalytic steps in a novel complex, the CΔhSlu7 complex. We provide evidence that this complex differs significantly in structure from the known spliceosomal complexes, yet is a functional intermediate between the catalytic steps of splicing. Together, our observations indicate that hSlu7 is required for a structural alteration of the spliceosome prior to the establishment of the catalytically active spliceosome for step II.

• Pre-mRNA splicing
• splicing factor
• catalytic step II
• spliceosome
• hSlu7

Footnotes

• ↵Corresponding author.

• E-MAIL rreed{at}hms.harvard.edu; FAX (617) 432-3091.

• • Received December 21, 1998.
  • Accepted February 16, 1998.

• Cold Spring Harbor Laboratory Press

•