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PMID: 9891067 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S.

Activation of the Lbc Rho exchange factor proto-oncogene by truncation of an extended C terminus that regulates transformation and targeting.

Molecular and cellular biology ·Vol. 19 ·No. 2 ·1999-02-00 ·Pages 1334-45

Sterpetti P, Hack AA, Bashar MP, Park B, Cheng SD, Knoll JH, Urano T, Feig LA, Toksoz D

Abstract

The human lbc oncogene product is a guanine nucleotide exchange factor that specifically activates the Rho small GTP binding protein, thus resulting in biologically active, GTP-bound Rho, which in turn mediates actin cytoskeletal reorganization, gene transcription, and entry into the mitotic S phase. In order to elucidate the mechanism of onco-Lbc transformation, here we report that while proto- and onco-lbc cDNAs encode identical N-terminal dbl oncogene homology (DH) and pleckstrin homology (PH) domains, proto-Lbc encodes a novel C terminus absent in the oncoprotein that includes a predicted alpha-helical region homologous to cyto-matrix proteins, followed by a proline-rich region. The lbc proto-oncogene maps to chromosome 15, and onco-lbc represents a fusion of the lbc proto-oncogene N terminus with a short, unrelated C-terminal sequence from chromosome 7. Both onco- and proto-Lbc can promote formation of GTP-bound Rho in vivo. Proto-Lbc transforming activity is much reduced compared to that of onco-Lbc, and a significant increase in transforming activity requires truncation of both the alpha-helical and proline-rich regions in the proto-Lbc C terminus. Deletion of the chromosome 7-derived C terminus of onco-Lbc does not destroy transforming activity, demonstrating that it is loss of the proto-Lbc C terminus, rather than gain of an unrelated C-terminus by onco-Lbc, that confers transforming activity. Mutations of onco-Lbc DH and PH domains demonstrate that both domains are necessary for full transforming activity. The proto-Lbc product localizes to the particulate (membrane) fraction, while the majority of the onco-Lbc product is cytosolic, and mutations of the PH domain do not affect this localization. The proto-Lbc C-terminus alone localizes predominantly to the particulate fraction, indicating that the C terminus may play a major role in the correct subcellular localization of proto-Lbc, thus providing a mechanism for regulating Lbc oncogenic potential.

MeSH Terms
A Kinase Anchor Proteins Adaptor Proteins, Signal Transducing Amino Acid Sequence Animals Base Sequence COS Cells Cell Transformation, Neoplastic/genetics Chimera/genetics Chromosomes, Human, Pair 15/genetics Chromosomes, Human, Pair 7/genetics Cricetinae DNA Primers/genetics DNA, Complementary/genetics GTP-Binding Proteins/genetics Gene Expression Regulation Gene Rearrangement Humans Minor Histocompatibility Antigens Molecular Sequence Data Proto-Oncogene Mas Proto-Oncogene Proteins/genetics Proto-Oncogenes RNA, Messenger/genetics,metabolism Sequence Deletion Sequence Homology, Amino Acid Tissue Distribution Transfection
Chemicals
A Kinase Anchor Proteins AKAP13 protein, human Adaptor Proteins, Signal Transducing DNA Primers DNA, Complementary MAS1 protein, human Minor Histocompatibility Antigens Proto-Oncogene Mas Proto-Oncogene Proteins RNA, Messenger GTP-Binding Proteins
Authors & Affiliations
9 authors, click to expand affiliations / ORCID
Sterpetti P
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Hack A A
Bashar M P
Park B
Cheng S D
Knoll J H
Urano T
Feig L A
Toksoz D
References (53)
53 references, click to expand
  1. Intracellular localization of the P21rho proteins.
    J Cell Biol. 1992 Nov;119(3):617-27 PMID: 1383236
  2. Cloning of cDNAs encoding human caldesmons.
    Gene. 1992 Mar 15;112(2):197-204 PMID: 1555769
  3. The small GTP-binding protein rho regulates the assembly of focal adhesions and actin stress fibers in response to growth factors.
    Cell. 1992 Aug 7;70(3):389-99 PMID: 1643657
  4. Identification of three developmentally controlled isoforms of human myosin heavy chains.
    Eur J Biochem. 1990 Apr 20;189(1):55-65 PMID: 1691980
  5. Monoclonal antibody mapping of structural and functional plectin epitopes.
    J Cell Biol. 1991 Feb;112(3):397-405 PMID: 1704007
  6. Catalysis of guanine nucleotide exchange on the CDC42Hs protein by the dbl oncogene product.
    Nature. 1991 Nov 28;354(6351):311-4 PMID: 1956381
  7. Leukemia and the disruption of normal hematopoiesis.
    Cell. 1991 Jan 25;64(2):337-50 PMID: 1988151
  8. Cloning and sequencing of rat plectin indicates a 466-kD polypeptide chain with a three-domain structure based on a central alpha-helical coiled coil.
    J Cell Biol. 1991 Jul;114(1):83-99 PMID: 2050743
  9. A region of proto-dbl essential for its transforming activity shows sequence similarity to a yeast cell cycle gene, CDC24, and the human breakpoint cluster gene, bcr.
    New Biol. 1991 Apr;3(4):372-9 PMID: 2065022
  10. Basic local alignment search tool.
    J Mol Biol. 1990 Oct 5;215(3):403-10 PMID: 2231712
  11. The N-terminal region of proto-dbl down regulates its transforming activity.
    Oncogene. 1989 Sep;4(9):1067-72 PMID: 2674851
  12. SR alpha promoter: an efficient and versatile mammalian cDNA expression system composed of the simian virus 40 early promoter and the R-U5 segment of human T-cell leukemia virus type 1 long terminal repeat.
    Mol Cell Biol. 1988 Jan;8(1):466-72 PMID: 2827008
  13. Molecular cloning and characterization of the human dbl proto-oncogene: evidence that its overexpression is sufficient to transform NIH/3T3 cells.
    EMBO J. 1988 Aug;7(8):2465-73 PMID: 3056717
  14. The ras gene family and human carcinogenesis.
    Mutat Res. 1988 May;195(3):255-71 PMID: 3283542
  15. The leucine zipper: a hypothetical structure common to a new class of DNA binding proteins.
    Science. 1988 Jun 24;240(4860):1759-64 PMID: 3289117
  16. Expression of normal and mutant ras proteins in human acute leukemia.
    Oncogene. 1987 May;1(2):157-65 PMID: 3325880
  17. ras gene activation in a minor proportion of the blast population in acute myeloid leukemia.
    Oncogene. 1987;1(4):409-13 PMID: 3330783
  18. Rapid and efficient site-specific mutagenesis without phenotypic selection.
    Proc Natl Acad Sci U S A. 1985 Jan;82(2):488-92 PMID: 3881765
  19. Point mutations define a sequence flanking the AUG initiator codon that modulates translation by eukaryotic ribosomes.
    Cell. 1986 Jan 31;44(2):283-92 PMID: 3943125
  20. Specific and high-affinity binding of inositol phosphates to an isolated pleckstrin homology domain.
    Proc Natl Acad Sci U S A. 1995 Nov 7;92(23):10472-6 PMID: 7479822
  21. The Rho family GTPases RhoA, Rac1, and CDC42Hs regulate transcriptional activation by SRF.
    Cell. 1995 Jun 30;81(7):1159-70 PMID: 7600583
  22. Expression cloning of lfc, a novel oncogene with structural similarities to guanine nucleotide exchange factors and to the regulatory region of protein kinase C.
    J Biol Chem. 1995 Aug 4;270(31):18388-95 PMID: 7629163
  23. Calcium activation of Ras mediated by neuronal exchange factor Ras-GRF.
    Nature. 1995 Aug 10;376(6540):524-7 PMID: 7637786
  24. An essential role for Rho, Rac, and Cdc42 GTPases in cell cycle progression through G1.
    Science. 1995 Sep 1;269(5228):1270-2 PMID: 7652575
  25. The structure of human trichohyalin. Potential multiple roles as a functional EF-hand-like calcium-binding protein, a cornified cell envelope precursor, and an intermediate filament-associated (cross-linking) protein.
    J Biol Chem. 1993 Jun 5;268(16):12164-76 PMID: 7685034
  26. Direct involvement of the small GTP-binding protein Rho in lbc oncogene function.
    J Biol Chem. 1995 Apr 21;270(16):9031-4 PMID: 7721814
  27. A role for Rac in Tiam1-induced membrane ruffling and invasion.
    Nature. 1995 May 25;375(6529):338-40 PMID: 7753201
  28. G beta gamma interactions with PH domains and Ras-MAPK signaling pathways.
    Trends Biochem Sci. 1995 Apr;20(4):151-6 PMID: 7770915
  29. Small GTP-binding proteins and the regulation of the actin cytoskeleton.
    Annu Rev Cell Biol. 1994;10:31-54 PMID: 7888179
  30. Pleckstrin homology domains bind to phosphatidylinositol-4,5-bisphosphate.
    Nature. 1994 Sep 8;371(6493):168-70 PMID: 8072546
  31. Requirement for Ras in Raf activation is overcome by targeting Raf to the plasma membrane.
    Nature. 1994 Jun 2;369(6479):411-4 PMID: 8196769
  32. The PH domain: a common piece in the structural patchwork of signalling proteins.
    Trends Biochem Sci. 1993 Sep;18(9):343-8 PMID: 8236453
  33. Proteins regulating Ras and its relatives.
    Nature. 1993 Dec 16;366(6456):643-54 PMID: 8259209
  34. Novel human oncogene lbc detected by transfection with distinct homology regions to signal transduction products.
    Oncogene. 1994 Feb;9(2):621-8 PMID: 8290273
  35. Identification and molecular characterization of E-MAP-115, a novel microtubule-associated protein predominantly expressed in epithelial cells.
    J Cell Biol. 1993 Oct;123(2):357-71 PMID: 8408219
  36. Molecular analysis of the INCENPs (inner centromere proteins): separate domains are required for association with microtubules during interphase and with the central spindle during anaphase.
    J Cell Biol. 1993 Oct;123(2):373-85 PMID: 8408220
  37. Identification of a ten-amino acid proline-rich SH3 binding site.
    Science. 1993 Feb 19;259(5098):1157-61 PMID: 8438166
  38. Ral-GTPases mediate a distinct downstream signaling pathway from Ras that facilitates cellular transformation.
    EMBO J. 1996 Feb 15;15(4):810-6 PMID: 8631302
  39. Identification of a novel human Rho protein with unusual properties: GTPase deficiency and in vivo farnesylation.
    Mol Cell Biol. 1996 Jun;16(6):2689-99 PMID: 8649376
  40. Expression cloning of lsc, a novel oncogene with structural similarities to the Dbl family of guanine nucleotide exchange factors.
    J Biol Chem. 1996 Aug 2;271(31):18643-50 PMID: 8702517
  41. The pleckstrin homology domain mediates transformation by oncogenic dbl through specific intracellular targeting.
    J Biol Chem. 1996 Aug 9;271(32):19017-20 PMID: 8702569
  42. The N-terminal pleckstrin, coiled-coil, and IQ domains of the exchange factor Ras-GRF act cooperatively to facilitate activation by calcium.
    Mol Cell Biol. 1996 Sep;16(9):4888-96 PMID: 8756648
  43. The Dbl family of oncogenes.
    Curr Opin Cell Biol. 1996 Apr;8(2):216-22 PMID: 8791419
  44. Identification of a novel guanine nucleotide exchange factor for the Rho GTPase.
    J Biol Chem. 1996 Oct 11;271(41):25452-8 PMID: 8810315
  45. Lfc and Lsc oncoproteins represent two new guanine nucleotide exchange factors for the Rho GTP-binding protein.
    J Biol Chem. 1996 Nov 1;271(44):27374-81 PMID: 8910315
  46. Transformation by Rho exchange factor oncogenes is mediated by activation of an integrin-dependent pathway.
    EMBO J. 1996 Dec 2;15(23):6525-30 PMID: 8978679
  47. Phosphotyrosine-dependent activation of Rac-1 GDP/GTP exchange by the vav proto-oncogene product.
    Nature. 1997 Jan 9;385(6612):169-72 PMID: 8990121
  48. Targeting of Tiam1 to the plasma membrane requires the cooperative function of the N-terminal pleckstrin homology domain and an adjacent protein interaction domain.
    J Biol Chem. 1997 Nov 7;272(45):28447-54 PMID: 9353304
  49. A novel Cdc42Hs mutant induces cellular transformation.
    Curr Biol. 1997 Oct 1;7(10):794-7 PMID: 9368762
  50. Distinct roles for DH and PH domains in the Lbc oncogene.
    Oncogene. 1997 Dec 4;15(23):2827-31 PMID: 9419973
  51. Rho GTPases and the actin cytoskeleton.
    Science. 1998 Jan 23;279(5350):509-14 PMID: 9438836
  52. Role of substrates and products of PI 3-kinase in regulating activation of Rac-related guanosine triphosphatases by Vav.
    Science. 1998 Jan 23;279(5350):558-60 PMID: 9438848
  53. Coupling of Ras and Rac guanosine triphosphatases through the Ras exchanger Sos.
    Science. 1998 Jan 23;279(5350):560-3 PMID: 9438849
Article Info
Journal
Molecular and cellular biology
Abbr.
Mol Cell Biol
ISSN
0270-7306
DOI
10.1128/MCB.19.2.1334
Published
1999-02-00
Pages
1334-45
Language
English
Region
United States
NLM ID
8109087
PMCID
PMC116062
Subset
IM
Grants
NCI NIH HHS · CA62029 · United States
NIGMS NIH HHS · GM47707 · United States
NICHD NIH HHS · HD 18658 · United States
Databases
GENBANK
AF127481
Corrections
ErratumIn
-
External Links
PubMed source DOI: 10.1128/MCB.19.2.1334 PMC Full Text View journal details
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