FIGURE 6.

xPTB prevents the activity of UTE in non muscle cells. A, mutant minigenes deleted for UTE (ΔUTE) and wild-type (WT) minigenes, driven by the keratin promoter, were injected in Xenopus embryo alone (−) or together with control morpholino (Co Mo) or xPTB-Mo. The steady-state level of xPTB was checked by Western blot using a xPTB antiserum. xPTB is indicated by an arrow, and the nonspecific cross-reacting band indicated by a star was used as a loading control. The mRNA splicing pattern was assayed by 3′-RACE-PCR using a ³²P-oligonucleotide specific to the keratin minigene constructs. B, the wild-type and ΔUTE minigenes driven by the SV40 promoter were injected into oocyte nuclei alone or with increasing amounts of 150PY competitor RNA. The mRNA splicing pattern was assayed by 3′-RACE-PCR using a ³²P-oligonucleotide specific to SV40 minigene constructs. A and B, quantification was performed on a PhosphorImager to yield the proportion of each product given in the table below. ND, not detected.