CUS2, a yeast homolog of human Tat-SF1, rescues function of misfolded U2 through an unusual RNA recognition motif.
A screen for suppressors of a U2 snRNA mutation identified CUS2, an atypical member of the RNA recognition motif (RRM) family of RNA binding proteins. CUS2 protein is associated with U2 RNA in splicing extracts and interacts with PRP11, a subunit of the conserved splicing factor SF3a. Absence of CUS2 renders certain U2 RNA folding mutants lethal, arguing that a normal activity of CUS2 is to help refold U2 into a structure favorable for its binding to SF3b and SF3a prior to spliceosome assembly. Both CUS2 function in vivo and the in vitro RNA binding activity of CUS2 are disrupted by mutation of the first RRM, suggesting that rescue of misfolded U2 involves the direct binding of CUS2. Human Tat-SF1, reported to stimulate Tat-specific, transactivating region-dependent human immunodeficiency virus transcription in vitro, is structurally similar to CUS2. Anti-Tat-SF1 antibodies coimmunoprecipitate SF3a66 (SAP62), the human homolog of PRP11, suggesting that Tat-SF1 has a parallel function in splicing in human cells.
Center for the Molecular Biology of RNA, Biology Department, University of California, Santa Cruz, Santa Cruz, California 95064, USA.
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D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012326:RNA Splicing; D012331:RNA, Fungal / Q000737:chemistry / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000737:chemistry* / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*
C114067:CUS2 protein, S cerevisiae; C101819:HTATSF1 protein, human; D012331:RNA, Fungal; D012342:RNA, Small Nuclear; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators