Lbc proto-oncogene product binds to and could be negatively regulated by metastasis suppressor nm23-H2.
Lbc was identified as transforming gene from human leukemic cells and encodes Rho type guanine nucleotide exchange factor with 47kDa molecular weight. We isolated overlapping cDNAs of Lbc from human lung tissue. Full-length Lbc cDNA encodes 309kDa huge protein with Ht31 PKA anchoring motif, Dof domain, C1 domain, and coiled-coil structure. In order to analyze the regulatory mechanism of its activity, we searched for binding proteins. By yeast two-hybrid screening, we identified metastasis suppressor nm23-H2 as binding protein, which interacts with amino-terminal region of Lbc containing Dof domain. nm23 gene family encodes nucleoside diphosphate kinase, however, the binding of nm23-H2 to Lbc was independent of kinase activity. nm23-H1, which binds to Rac-specific GEF Tiam1, could not bind to Lbc suggesting nm23-H2 would be specific regulator for Lbc. Expression of nm23-H2 in cells leads to decrease the amount of GTP-bound Rho and suppress stress fiber formation stimulated by expression of Lbc. Our data suggest that metastasis suppressor nm23-H2 could regulate Lbc negatively by binding to amino-terminal region of Lbc proto-oncogene product.
Iwashita
Shinki
S
Graduate School of Science and Technology, Kobe University, 1-1Rokkodai-cho Nada, Kobe 657-8501, Japan.
Fujii
Makiko
M
Mukai
Hideyuki
H
Ono
Yoshitaka
Y
Miyamoto
Masaaki
M
D054758:A Kinase Anchor Proteins; D008841:Actin Cytoskeleton / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000502:physiology; D051379:Mice; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D054778:NM23 Nucleoside Diphosphate Kinases; D009701:Nucleoside-Diphosphate Kinase; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000737:chemistry* / Q000378:metabolism*
D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; D048868:Adaptor Proteins, Signal Transducing; C000715470:MAS1 protein, human; D015778:Minor Histocompatibility Antigens; D054778:NM23 Nucleoside Diphosphate Kinases; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; C517938:NME1 protein, human; C517939:Nme1 protein, mouse; D009701:Nucleoside-Diphosphate Kinase