N. Lehming et al., INTERACTIONS OF A REL PROTEIN WITH ITS INHIBITOR, Proceedings of the National Academy of Sciences of the United Statesof America, 92(22), 1995, pp. 10242-10246
Cactus, a Drosophila homologue of I kappa B, binds to and inhibits Dor
sal, a homologue of the p50 and p65 components of NF-kappa B. We descr
ibe experiments in yeast with various Dorsal and Cactus derivatives sh
owing that Cactus blocks the DNA binding and nuclear localization func
tions of Dorsal. In contrast, Dorsal's transcriptional activating regi
on is functional in the Dorsal-Cactus complex. We identify two Dorsal
mutants, Dorsal C233R and Dorsal S234P, that escape Cactus inhibition
in vivo, and we show that these mutants fail to interact with Cactus i
n vitro. From this and data of others, we identify the likely surface
of Dorsal that binds Cactus. We also describe a modified PCR mutagenes
is procedure, easier to use than conventional methods, that produces a
library of high complexity.