INTERACTION BETWEEN THE HUMAN NUCLEAR CAP-BINDING PROTEIN COMPLEX ANDHNRNP-F

hnRNP F was identified in a screen for proteins that interact with hum an CBP80 and CBP20, the components of the nuclear cap-binding complex (CBC). In vitro interaction studies showed that hnRNP F can bind to bo th CBP20 and CBP80 individually. hnRNP F and CBC bind independently to RNA, but hnRNP F binds preferentially to CBC-RNA complexes rather tha n to naked RNA. The hnRNP H protein, which is 78% identical to hnRNP F and also interacts with both CBP80 and CBP20 in vitro, does not discr iminate between naked RNA and CBC-RNA complexes, showing that this eff ect is specific. Depletion of hnRNP F from HeLa cell nuclear extract d ecreases the efficiency of pre-mRNA splicing, a defect which can be pa rtially compensated by addition of recombinant hnRNP F. Thus, hnRNP F is required for efficient pre-mRNA splicing in vitro and may participa te in the effect of CBC on pre-mRNA splicing.