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cDNA sequence of the rat U snRNP‐associated protein N: description of a potential Sm epitope.
Author(s) -
McAllister G.,
RobyShemkovitz A.,
Amara S. G.,
Lerner M. R.
Publication year - 1989
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1989.tb03489.x
Subject(s) - haven , section (typography) , library science , medical school , medicine , medical education , computer science , mathematics , combinatorics , operating system
Anti‐Sm antibodies from a patient with systemic lupus erythematosus (SLE) were used to isolate cDNA clones encoding the snRNP‐associated protein N from a rat brain derived cDNA library. The predicted primary structure of the 240 amino acid protein has a proline rich carboxyl terminus and shares a region of sequence similarity with other snRNP polypeptides, A and B/B‘. Anti‐Sm sera recognize a beta‐galactosidase fusion protein containing only the carboxyl‐terminal 80 amino acids of N; antibodies eluted from this fusion protein also react with A, B/B’ and N on immunoblots, suggesting that these proteins share an Sm epitope located within this segment. Polyclonal antibodies raised against a 23 amino acid synthetic peptide derived from this conserved region of N recognize A, N and B/B‘ on immunoblots and can immunoprecipitate the Sm class of U snRNAs. These results confirm that this sequence defines a potential Sm epitope. RNA blotting analyses demonstrate that a 1.6 kb mRNA expressed predominantly in brain encodes the N polypeptide in both rats and humans. At low stringency rat N cDNA also hybridizes to a 1.3 kb mRNA species which encodes B/B’, suggesting that N is structurally related to, but distinct from B/B‘. Although B/B’ proteins are thought to be expressed in all human cells, only N and B, but not B′, are observed on immunoblots of human brain proteins probed with anti‐Sm sera. The apparent difference in the complement of proteins associated with snRNP particles in human brain versus elsewhere suggests a possible mechanism for the regulation of brain‐specific mRNA splicing.