CPEB forms a dimer in mammalian cells. (A) CPEB-HA and CPEB-FLAG were co-expressed in HEK 293T cells followed by reciprocal co-immunoprecipitation (IP) with HA or FLAG antibodies and Western blotting with the same antibodies. These co-IPs demonstrate that CPEB forms a dimer. Actin served as an IP and loading control. (B) Extracts from CPEB-HA transfected HEK 293T were incubated with increasing amounts of formaldehyde, which was followed by immunoblotting for the HA epitope. Note that, with lower formaldehyde, a 130-kDa CPEB band was evident, which is the size of a CPEB dimer. N.T., nontransfected. (C) CPEB-HA and CPEB-FLAG were co-expressed in HEK 293T cells and cross-linked with 0.12% formaldehyde as in panel B. Stringent IP conditions were applied to minimize possible nonspecific adducts. The precipitate was then subjected to Western blotting with antibody for the HA and FLAG epitopes.
