Identification of a novel RalGDS-related protein as a candidate effector for Ras and Rap1.
Although Ras and Rap1 share interaction with common candidate effector proteins, Rap1 lacks the transforming activity exhibited by Ras proteins. It has been speculated that Rap antagonizes Ras transformation through the formation of nonproductive complexes with critical Ras effector targets. To understand further the distinct biological functions of these two closely related proteins, we searched for Rap1b-binding proteins by yeast two-hybrid screening. We identified multiple clones that encode the COOH-terminal sequences of a protein that shares sequence identity with RalGDS and RGL, which we have designated RGL2. A 158-amino acid COOH-terminal fragment of RGL2 (RGL2 C-158) bound to Ras superfamily proteins which shared identical effector domain sequences with Rap1 (Ha-Ras, R-Ras, and TC21). RGL2 C-158 binding was impaired by effector domain mutations in Rap1b and Ha-Ras. Furthermore, RGL2 C-158 bound exclusively to the GTP-, but not the GDP-bound form of Ha-Ras. Finally, coexpression of RGL2 C-158 impaired oncogenic Ras activation of transcription from a Ras-responsive promoter element and focus-forming activity in NIH 3T3 cells. We conclude that RGL2 may be an effector for Ras and/or Rap proteins.
Peterson
S N
SN
Division of Cell Biology, Glaxo Wellcome Inc., Research Triangle Park, North Carolina 27709, USA.
Trabalzini
L
L
Brtva
T R
TR
Fischer
T
T
Altschuler
D L
DL
Martelli
P
P
Lapetina
E G
EG
Der
C J
CJ
White
G C
GC
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002461:Cell Line, Transformed; D018076:DNA, Complementary; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D020726:ral Guanine Nucleotide Exchange Factor; D020668:rap GTP-Binding Proteins; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; C490771:RGL1 protein, human; C097104:Rgl1 protein, mouse; D020726:ral Guanine Nucleotide Exchange Factor; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins; D018631:ras Proteins