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Adenovirus E1A requires c-Ras for full neoplastic transformation or suppression of differentiation of murine

J Cao1, R Arulanandam, A Vultur

  • 1Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada.

Molecular Carcinogenesis
|February 14, 2007
PubMed

Insights

Adenovirus-5 E1A protein blocks preadipocyte differentiation and induces apoptosis. Cellular Ras protooncogene product (Ras) is crucial for E1A function, as its downregulation prevents E1A-mediated differentiation suppression and neoplastic transformation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • Adenovirus-5 E1A (E1A) gene products activate E2F and inhibit murine preadipocyte differentiation.
  • Higher E1A levels induce apoptosis and can lead to neoplastic transformation.
  • The role of cellular Ras protooncogene product (Ras) in E1A's function remains unclear.

Purpose of the Study:

  • To investigate the role of Ras in E1A-mediated suppression of preadipocyte differentiation and neoplastic transformation.
  • To determine if Ras downregulation affects E1A's ability to activate E2F or induce apoptosis.

Main Methods:

  • Adenovirus-5 E1A was expressed in C3H10T(1/2) preadipocytes with inducible or constitutive antisense ras gene constructs (Ras-knockdowns).
  • Differentiation suppression, neoplastic transformation, E2F activation, and apoptosis induction were assessed.
  • E1A protein levels were monitored during differentiation.

Main Results:

  • Ras-knockdown preadipocytes resisted E1A-mediated differentiation suppression and neoplastic transformation, even at high E1A levels.
  • Ras downregulation did not impact E1A's E2F activation.
  • E1A protein levels and apoptosis-inducing capacity significantly decreased during differentiation progression in Ras-knockdown cells.

Conclusions:

  • Cellular Ras is essential for E1A's ability to suppress preadipocyte differentiation and induce neoplastic conversion.
  • Ras acts as an integral component in the E1A signaling pathway, despite E1A's primary nuclear targets.
  • These findings reveal a novel cytoplasmic role for Ras in mediating the oncogenic functions of E1A.

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