Figure 1.

Crosslinking profile of the BP-derivatized 5′SS RNA. (A) Structure of the ³²P-labeled, BP-derivatized 14-nt 5′SS RNA. (B) The 5′SS RNA was incubated with HeLa NE in the absence (lanes 1, 3) or presence (lanes 2, 4) of ATP and in the presence (lanes 1, 2) or absence (lanes 3, 4) of U1-blocking DNA. (C) Wild-type 5′SS RNA (WT) or 5′SS RNAs with single point mutations at intron pos. +1 or +2 was incubated with HeLa NE in the absence of ATP or U1-blocking DNA. (D) The 5′SS crosslinks were immunoprecipitated under denaturing conditions with α-Sm (Y12) antibodies. Crosslinked products were resolved in 11% SDS gels. Positions of the molecular weight markers and the 5′SS crosslinks are indicated.