Abstract
We have purified three new human U4/U6-snRNP proteins from HeLa cells. The three proteins formed a tightly bound complex and behaved as a single species throughout the purification. All three proteins have been identified by peptide sequencing, and full-length cDNA sequences have been obtained for all of them. Two of the proteins are homologues of the Saccharomyces cerevisiae splicing factors Prp3 and Prp4, and the third protein is a cyclophilin. Both the human and S. cerevisiae Prp4 proteins have seven repeats of the WD motif and likely fold into structures very similar to those of the beta subunits of G proteins. The human Prp3 protein is highly basic and is closely related to S. cerevisiae Prp3 only in its carboxyl-terminal half. The human homologues of Prp3 and Prp4 are part of a stable complex in the absence of RNA. The third protein in the complex is a new cyclophilin. Cyclophilins have been proposed to act as chaperones in a variety of cellular processes, and we discuss some possible roles of this U4/U6 snRNP-associated cyclophilin.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Cloning, Molecular
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DNA, Complementary / genetics
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HeLa Cells
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Humans
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Molecular Sequence Data
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Molecular Weight
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Nuclear Proteins / chemistry*
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Nuclear Proteins / genetics
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Nuclear Proteins / isolation & purification
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Nuclear Proteins / metabolism
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Peptides / chemistry
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Peptidylprolyl Isomerase / chemistry*
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Peptidylprolyl Isomerase / genetics
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Peptidylprolyl Isomerase / isolation & purification
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Peptidylprolyl Isomerase / metabolism
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Protein Serine-Threonine Kinases / chemistry*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / isolation & purification
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Protein Serine-Threonine Kinases / metabolism
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RNA Splicing Factors
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Ribonucleoprotein, U4-U6 Small Nuclear / chemistry*
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Ribonucleoprotein, U4-U6 Small Nuclear / genetics
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Ribonucleoprotein, U4-U6 Small Nuclear / isolation & purification
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Ribonucleoprotein, U4-U6 Small Nuclear / metabolism*
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Saccharomyces cerevisiae / chemistry
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Saccharomyces cerevisiae Proteins*
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Sequence Analysis
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Sequence Analysis, DNA
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Sequence Homology, Amino Acid
Substances
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DNA, Complementary
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Nuclear Proteins
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PRP3 protein, S cerevisiae
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PRPF3 protein, human
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PRPF4 protein, human
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Peptides
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RNA Splicing Factors
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Ribonucleoprotein, U4-U6 Small Nuclear
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Saccharomyces cerevisiae Proteins
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PRP4 protein, S cerevisiae
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Protein Serine-Threonine Kinases
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Peptidylprolyl Isomerase
Associated data
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GENBANK/AF016369
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GENBANK/AF016370
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GENBANK/AF016371