Analysis of U1snRNP-specific A protein cross-linked complexes.

The organization of the U1snRNP-specific A protein (34 kDa) has been analyzed by 12 and 16 A thiol-reversible chemical cross-linking and Western blotting. A-containing cross-linked complexes had molecular masses of 43, 47, 56, 62, 67, 105 and 125 kDa. None of these complexes could be cross-linked following ribonuclease digestion, suggesting that UsnRNA may play important roles in the spatial organization of A and other proteins. Moreover, the data suggest that A is proximal to, and may have interactions with, UsnRNP-specific proteins C and 70 kDa as well as with UsnRNP-common proteins B, E and G.