Primary structure of a human small nuclear ribonucleoprotein polypeptide as deduced by cDNA analysis.
Anti-Sm is an antibody specificity often associated with the autoimmune disease systemic lupus erythematosus. The polypeptides Sm-B'/B (estimated molecular mass 27 and 26 kDa, respectively) are primary targets of Sm antibodies. Sm-B'/B are part of the core polypeptides of small ribonucleoprotein particles (snRNP) involved in pre-mRNA splicing. Sm-B'/B share the same amino-terminal sequence as we determined by microsequence analyses of the purified polypeptides. Oligonucleotide probes based on that sequence were used to isolate seven clones from a human lymphoblastoid cDNA library in lambda gt10. The clones contained a single coding region for a protein of approximately 25 kDa. The predicted amino-terminal sequence was identical to that of the isolated Sm-B'/B polypeptides. In vitro translation experiments produced a protein immunoreactive with human polyclonal anti-Sm antibodies. The isolation of only one unique cDNA sequence suggests that Sm-B'/B may be post-translational variants encoded by a single message. The specific structural features which distinguish Sm-B' from Sm-B have yet to be determined. Northern blot analysis confirmed the diverse tissue and species distribution expected for these immunologically conserved polypeptides. The Sm-B'/B primary sequence is rich in proline (20%) and glycine (15%) residues. The prolines are concentrated in the carboxyl-terminal half of the protein and display a repetitive unit that is shared with other snRNP and nucleic acid binding proteins. Analysis of these arrays suggests an eight residue proline-rich consensus sequence with potential as either an RNA binding domain, or as a site of protein/protein interaction.
Rokeach
L A
LA
Agouron Institute, La Jolla, California 92037.
Jannatipour
M
M
Haselby
J A
JA
Hoch
S O
SO
D000595:Amino Acid Sequence; D001324:Autoantigens / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification*; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004247:DNA / Q000302:isolation & purification*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010452:Peptide Biosynthesis; D010455:Peptides / Q000235:genetics / Q000302:isolation & purification*; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012261:Ribonucleoproteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification*; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins
D001324:Autoantigens; D010455:Peptides; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins; D004247:DNA