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Molecular cloning of cDNAs encoding a guanine-nucleotide-releasing factor for Ras p21

C Shou1, C L Farnsworth, B G Neel

  • 1Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111.

Nature
|July 23, 1992
PubMed

Insights

Researchers identified a novel guanine-nucleotide-releasing factor (GRF) for Ras proteins, named p140Ras-GRF. This discovery advances understanding of Ras signaling pathways critical for cellular function.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Biochemistry

Background:

  • Cell surface receptor stimulation leads to active, GTP-bound Ras proteins, a crucial step in signal transduction.
  • Inhibiting Ras activation blocks receptor-mediated cellular functions, highlighting Ras's importance.
  • Ras activation requires GDP release, a rate-limiting step potentially catalyzed by guanine-nucleotide-releasing factors (GRFs).

Purpose of the Study:

  • To clone and characterize a guanine-nucleotide-releasing factor (GRF) specific for Ras proteins.
  • To investigate the functional domains and specificity of the identified Ras GRF.

Main Methods:

  • Cloning complementary DNAs from a rat brain library.
  • Sequence analysis to identify homologous regions with known GRFs (CDC25, Bcr, dbl).
  • In vitro assays to measure GDP release from various GTP-binding proteins (RasH, RasN, RalA, CDC42Hs).

Main Results:

  • Cloned a cDNA encoding a ~140 kDa GRF for Ras p21 (p140Ras-GRF).
  • The carboxy-terminal region of p140Ras-GRF showed similarity to CDC25 and accelerated GDP release from RasH and RasN p21 in vitro.
  • The amino-terminal region shared homology with Bcr and dbl, known GRFs for other GTPases.

Conclusions:

  • p140Ras-GRF is a novel guanine-nucleotide-releasing factor specific for Ras proteins.
  • Its distinct functional domains suggest a role in regulating Ras-mediated signal transduction pathways.
  • Understanding p140Ras-GRF function is key to elucidating diverse cellular processes controlled by Ras.

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