FIG. 7.

Oligomerization of Siah-1 proteins requires C-terminal sequences, and degradation function requires the RING finger domain. Regulation of HA-SIAH1-dR protein expression by SIAH1. COS-1 cells were cotransfected with constructs encoding an HA-tagged RING-deleted Siah-1 mutant (i.e., Siah-1-dR) (lanes 1 to 7) and Flag-tagged wild-type and mutant Siah-1 proteins (lanes 2 to 7, and indicated), or empty vector (lane 1). The expression of HA-Siah-1-dR was analyzed by Western blotting with anti-HA monoclonal antibody 12CA5. The same blot was then stripped and blotted with anti-actin polyclonal antibody C11 to verify equivalent loading in the lanes. The migration positions (in kilodaltons) of selected molecular mass markers are indicated to the left of the blots.