A new cyclophilin and the human homologues of yeast Prp3 and Prp4 form a complex associated with U4/U6 snRNPs.
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.
Horowitz
D S
DS
Cold Spring Harbor Laboratory, New York 11724, USA. dhorowit@mx3.usuhs.mil
Kobayashi
R
R
Krainer
A R
AR
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000072260:RNA Splicing Factors; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins; D017421:Sequence Analysis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D009687:Nuclear Proteins; C491564:PRP3 protein, S cerevisiae; C108507:PRPF3 protein, human; C489982:PRPF4 protein, human; D010455:Peptides; D000072260:RNA Splicing Factors; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; C083212:PRP4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D019696:Peptidylprolyl Isomerase