The invention provides novel compositions comprising a Smad protein and an isolated
protein component of the proteasome-mediated degradation pathway. The invention
also provides novel compositions comprising a Smad1 protein and a substrate for
proteasome-mediated degradation. The invention also provides methods of screening
for compounds that modulate the interaction between the proteins comprising these
compositions. The invention also provides methods of screening for compounds that
modulate the activity of the proteins comprising these compositions. The invention
also provides methods of detecting proteasome-mediated degradation of novel Smad
interacting proteins. A further aspect of the invention is a kit for detecting
proteasome-mediated degradation of novel Smad interacting proteins. The invention
also provides methods of treating diseases which are associated with aberrant levels
of activity of a TGF- superfamily member.
