Abstract
Here, we report the identification and characterization of a new member of the RalGDS-family, which is widely expressed and interacts strongly and selectively with the GTP-bound forms of M-Ras and p21 Ras. This Ras pathway modulator (RPM), also termed RGL3, exhibited Ras-binding and catalytic domains typical of the RalGDS-family of guanine nucleotide exchange factors, and was most similar to Rlf (RalGDS-like factor), but was distinguished by a unique proline-rich region with multiple candidate SH3-domain binding sites. RPM/RGL3 resembled AF-6 and Nore1 in interacting strongly with constitutively active M-Ras and p21 Ras. In contrast to Rlf, transiently expressed RPM/RGL3 did not activate an Elk-1-inducible reporter gene alone or in combination with activated p21 Ras, but strongly inhibited induction of this reporter gene by co-expression of activated H-Ras or MEKK-1. This inhibitory effect was independent of the Ras binding domain and required a second signal provided by p21 Ras or MEKK-1, but not Raf-1 or M-Ras. Expression of RPM/RGL3 also strongly inhibited cell growth of fibroblasts transformed by an activated Src Y527F. Thus, RPM/RGL3 is a novel potential effector of both p21 Ras and M-Ras with the novel function of negatively regulating Elk-1-dependent gene induction downstream of p21 Ras or MEKK-1.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3T3 Cells
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Amino Acid Sequence
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Animals
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Binding Sites
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Cell Division / genetics
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Cells, Cultured
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DNA-Binding Proteins*
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Humans
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JNK Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinase 1*
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Mice
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Mitogen-Activated Protein Kinases / metabolism
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Molecular Sequence Data
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Monomeric GTP-Binding Proteins / genetics
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Monomeric GTP-Binding Proteins / metabolism*
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Phosphorylation
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-raf / metabolism
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Proto-Oncogene Proteins p21(ras) / genetics*
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Proto-Oncogene Proteins p21(ras) / metabolism
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Sequence Homology, Amino Acid
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Transcription Factors*
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ets-Domain Protein Elk-1
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p38 Mitogen-Activated Protein Kinases
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ral Guanine Nucleotide Exchange Factor / genetics*
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ral Guanine Nucleotide Exchange Factor / metabolism*
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ras Proteins
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src Homology Domains
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src-Family Kinases / genetics
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src-Family Kinases / metabolism
Substances
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DNA-Binding Proteins
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ELK1 protein, human
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Elk1 protein, mouse
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Proto-Oncogene Proteins
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Rgl3 protein, mouse
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Transcription Factors
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ets-Domain Protein Elk-1
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ral Guanine Nucleotide Exchange Factor
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src-Family Kinases
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-raf
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinase 1
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MAP3K1 protein, human
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Map3k1 protein, mouse
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Mras protein, mouse
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HRAS protein, human
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Monomeric GTP-Binding Proteins
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Proto-Oncogene Proteins p21(ras)
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ras Proteins