Splicing factor SF3a60 is the mammalian homologue of PRP9 of S.cerevisiae: the conserved zinc finger-like motif is functionally exchangeable in vivo

Abstract

A cDNA encoding the 60 kDa subunit of mammalian splicing factor SF3a has been isolated. The deduced protein sequence reveals a 30% identity to the PRP9 splicing protein of the yeast S.cerevisiae. The highest homology is present in a zinc finger-like region in the C-terminal domain of both proteins. The PRP9 zinc finger-like motif has been replaced by the equivalent region of mammalian SF3a60. The chimeric protein rescues the temperature-sensitive phenotype of the prp9-1 mutant strain demonstrating that not only the structure but also the function of this domain has been conserved during evolution.

Evidence that sequence-independent binding of highly conserved U2 snRNP proteins upstream of the branch site is required for assembly of spliceosomal complex A.

“…1C; SAP 145 amino acids 477--631} where the identity is 47%. The identity between SAP 145 and ySAP 145 is equal to, or greater than, that found between the yeast and mammalian SF3a subunits (Bennett and Reed 1993;Chiara et al 1994;Kramer et al 1994Kramer et al , 1995.…”

“…However, this complex has been shown to contain all three subunits of SF3a; the essential yeast pre-mRNA processing (PRP) factors PRP9, PRPll, and PRP21 correspond to SAPs 61, 62, and 114 {for reviews, see Hodges and Beggs 1994;Newman 1994}. cDNAs encoding SAPs 61 (Chiara et al 1994;Kramer et al 1994), 62 {Bennett and Reed 1993), and SF3a 12° (Kramer et al 1995) have been isolated and the deduced amino acid sequences found to be -25% identical to the corresponding yeast factors. Although it is not yet known whether the yeast SF3a homologs UV cross-link to pre-mRNA, the protein-protein interactions between the SF3a subunits appear to be conserved.…”

“…Although it is not yet known whether the yeast SF3a homologs UV cross-link to pre-mRNA, the protein-protein interactions between the SF3a subunits appear to be conserved. In mammals, SAPs 61 and 62 both interact with SAP 114, while in yeast PRPs 9 and 11 both interact with PRP21 (Bennett and Reed 1993;Chiara et al 1994;Kramer et al 1994Kramer et al , 1995. Despite the apparent conservation between yeast and mammals in assembly of the A complex, no yeast homologs of any of the SF3b subunits have been reported.…”

A Novel Nuclear Receptor Corepressor Complex, N-CoR, Contains Components of the Mammalian SWI/SNF Complex and the Corepressor KAP-1

“…Interestingly, several of the proteins that consistently copurified with N-CoR have been found as intrinsic components of unrelated, yet biologically important complexes. For example, SAP 130 and SF3a120 are subunits of protein complexes essential for spliceosome assembly (38,39). However, a function for SAP 130 and SF3a120 in transcriptional regulation has not been previously uncovered.…”

Mutation in the prp12 + gene encoding a homolog of SAP130/SF3b130 causes differential inhibition of pre-mRNA splicing and arrest of cell-cycle progression in Schizosaccharomyces pombe

“…To identify novel factors involved in pre-mRNA splicing, we and others have isolated prp (pre-mRNA processing) mutants of fission yeast Schizosaccharomyces pombe, which are defective in pre-mRNA splicing at the nonpermissive temperature+ So far, 14 prp mutants (prp1-prp14 ) have been isolated in S. pombe (Potashkin & Frendewey, 1989;Rosenberg et al+, 1991;Urushiyama et al+, 1996;Potashkin et al+, 1998)+ At the nonpermissive temperature, these mutants are defective in pre-mRNA splicing and accumulate pre-mRNAs in cells+ Interestingly, cell bodies in 8 of 14 prp mutants are elongated at the nonpermissive temperature, a typical phenotype observed in cell division cycle (cdc) mutants (Urushiyama et al+, 1996;Potashkin et al+, 1998)+ Expression of the cdc-like phenotype at the nonpermissive temperature in these mutants indicates a possible relation between pre-mRNA splicing and cell-cycle progression+ The prp1 ϩ gene was found to encode a protein with a TPR-motif (Urushiyama et al+, 1997) and to be allelic with zer1 (zero1), which was independently identified as a G0 arrest mutation (K+ Okazaki & H+ Okayama, unpubl+ results)+ The prp2 ϩ gene encodes spU2AF 59 , a fission yeast homolog of the human U2AF large subunit U2AF 65 (Potashkin et al+, 1993;Wentz-Hunter & Potashkin, 1996)+ The prp4 ϩ gene product is predicted to be a serine/threonine kinase (Alahari et al+, 1993;Groß et al+, 1997)+ The prp10 ϩ gene encodes a fission yeast homolog of SAP155/SF3b155, a subunit of the splicing factor complex SF3 associated with U2 snRNP (Habara et al+, 1998)+ Mutants of these four genes do not exhibit the cdc-like phenotype at the nonpermissive temperature+ On the other hand, two of the genes responsible for prp mutations with the cdc phenotype (prp5 and prp8) were cloned+ The prp5 ϩ gene encodes a WD repeat protein (McDonald et al+, 1999)+ Physical and genetic interactions between Prp5p and Cdc5p were also reported (McDonald et al+, 1999)+ The prp8 ϩ gene, the mutant of which exhibits the typical cdc phenotype, was found to be identical with the cdc28 ϩ gene encoding a DEAH-box RNA helicase (Lundgren et al+, 1996)+ However, exact mechanisms whereby defects in pre-mRNA splicing cause cell-cycle blocks in these mutants are still unknown+ SF3 is a U2 snRNP-associated multisubunit complex required for binding of U2 snRNA to the branch site+ It consists of two subcomplexes, SF3a and SF3b (reviewed in Krämer, 1996;Burge et al+, 1999)+ SF3a and SF3b contain three (SAP61/SF3a60, SAP62/SF3a66, and SAP114/SF3a120) and four subunits (SAP49/ SF3b50, SAP130/SF3b130, SAP145/SF3b145, and SAP155/SF3b155), respectively (Krämer et al+, 1994;…”