The small nuclear ribonucleoproteins that react with anti-Sm and anti-RNP antibodies

We have examined the polypeptide pattern of small nuclear ribonucleoprotein particles that react with monoclonal anti-Sm antibodies or polyclonal anti-(U1)RNP antibodies. The fresh nuclear extracts analyzed were prepared from human cells that had been pulse-chased with a mixture of 15 3H-labeled amino acids. In contrast to previous reports in the literature, the apparent molecular weights of the major polypeptides that remained in the 1 M NaCl-washed ribonucleoprotein-antibody complexes were approximately 80000, 55000, 28000, 25000, 14000 and 9000, when probed with monoclonal anti-Sm antibodies, and about 69000, 58000 and 35000, when polyclonal anti-(U1)RNP antibodies were used.