Analysis of U1snRNP‐specific A protein cross‐linked complexes

Abstract
The organization of the UlsnRNP‐specific A protein (34 kDa) has been analyzed by 12 and 16 Å 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.