Human β-hemaglobin pre-mRNA splicing by Tip110 and its mutants. 32P-labeled human β-hemaglobin minigene pre-mRNA was incubated with Hela nuclear extract in the presence of 10 (+) or 50 ng (++) recombinant GST-Tip110 (lanes 2 and 3), GST-Tip110s (lanes 4 and 5), GST-ΔNLS (lanes 6 and 7), or GSTΔRRM (lanes 8 and 9). Recombinant GST protein (50 ng) was included as a control (lane 1). The reaction mixtures were separated on 8% denaturing PAGE (a). The symbols on the left are pre-mRNA and its splicing products. Splicing was quantitated by densitometric scanning of the intronless spliced RNA product on the autoradiography, the spliced RNA product in the reaction containing GST (lane 1) was set as the reference to calculate the relative level of pre-mRNA splicing (b).