Fig. 2. Immunohistochemistry of polyadenylation/translation factors in maturing mouse oocytes. Oocytes with an intact GV, or those cultured for 6 (usually at MI), or 16.5 (MII) hours were immunostained with antibodies directed against CPEB, IAK1 (Eg2), the 100 kDa subunit of CPSF, PAP and maskin (the signals for these proteins are red; IAKI is in green). The oocytes were also counterstained with DAPI (blue). Each immunostaining procedure was performed on at least 30 oocytes. Western blots of GV stage oocyte protein were probed with the same antibodies noted above; in each case, only a single immunoreactive species was observed. No signal was observed in either the immunofluorescence experiment or in the western blot experiment when preimmune serum was used as the source for the first antibody (data not shown).