Fig. 5. Y14 constitutes a cytoplasmic mRNP complex while Aly/REF dissociates during or immediately after export. (A) Immunoprecipi tations and RNA analysis were performed following nuclear injection of ³²P-labeled Ad2 pre-mRNA. Oocytes were incubated for 45 min before dissection. Anti-Y14 (4C4), anti-Aly (11G5) and control antibodies (SP2/0) were used for immunoprecipitation. (B) Immunoprecipitations and western blotting were carried out on the nucleoplasm and cytoplasm of HeLa cells. The fractions were pretreated with 10 µg/ml RNase A for 20 min before immunoprecipitation. Anti-Y14 (4C4), anti-Aly (11G5) and control non-immune antibodies (SP2/0) were used for immunoprecipitations. For western blotting, anti-Aly (11G5) and anti-Y14 antibodies (1F12) were used.