The spliceosome assembly pathway in mammalian extracts.
A mammalian splicing commitment complex was functionally defined by using a template commitment assay. This complex was partially purified and shown to be a required intermediate for complex A formation. The productive formation of this commitment complex required both splice sites and the polypyrimidine tract. U1 small nuclear ribonucleoprotein (snRNP) was the only spliceosomal U snRNP required for this formation. A protein factor, very likely U2AF, is probably involved in the formation of the splicing commitment complex. From the kinetics of appearance of complex A and complex B, it was previously postulated that complex A represents a functional intermediate in spliceosome assembly. Complex A was partially purified and shown to be a required intermediate for complex B (spliceosome) formation. Thus, a spliceosome pathway is for the first time supported by direct biochemical evidence: RNA+U1 snRNP+?U2 auxiliary factor+?Y----CC+U2 snRNP+Z----A+U4/6,5 snRNPs+ beta----B.
Jamison
S F
SF
Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710.
Crow
A
A
Garcia-Blanco
M A
MA
D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004247:DNA; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D012313:RNA; D012326:RNA Splicing; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*
D009687:Nuclear Proteins; D017411:Ribonucleoproteins, Small Nuclear; D012313:RNA; D004247:DNA