Thermal Sensitivity in NIH 3T3 Fibroblasts Transformed by the v-Fos Oncogene

Correlation with Reduced Accumulation of 68-kDa and 25-kDa Stress Proteins After Heat Shock

Authors

  • Nathalie Fabre-Jonca,

    1. Laboratoire du stress cellulaire, Centre de Génétique Moléculaire et Cellulaire, CNRS UMR-106, Université Claude Bernard Lyon-I, Villeurbanne France
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  • Sandrine Gonin,

    1. Laboratoire du stress cellulaire, Centre de Génétique Moléculaire et Cellulaire, CNRS UMR-106, Université Claude Bernard Lyon-I, Villeurbanne France
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  • Chantal Diaz-Latoud,

    1. Laboratoire du stress cellulaire, Centre de Génétique Moléculaire et Cellulaire, CNRS UMR-106, Université Claude Bernard Lyon-I, Villeurbanne France
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  • Jean-Pierre Rouault,

    1. Unité d'Hémato-Oncologie Moléculaire, INSERM CJF 93 93-07, Hopital Edouard Herriot, Lyon, France
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  • AndréPatrick Arrigo

    Corresponding author
    1. Laboratoire du stress cellulaire, Centre de Génétique Moléculaire et Cellulaire, CNRS UMR-106, Université Claude Bernard Lyon-I, Villeurbanne France
      Correspondence to A.-P. Arrigo, Laboratoire du Stress Cellulaire, CNRS UMR 106, Centre de Génétique moléculaire, Université Claude Bernard, Lyon-I, 43, Bd du 11 Novembre, F-69622 Villeurbanne Cédex, France
      Fax:+33 72440555.
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Correspondence to A.-P. Arrigo, Laboratoire du Stress Cellulaire, CNRS UMR 106, Centre de Génétique moléculaire, Université Claude Bernard, Lyon-I, 43, Bd du 11 Novembre, F-69622 Villeurbanne Cédex, France
Fax:+33 72440555.

Abstract

The effect of v-fos transformation on the cellular response to heat shock has been investigated. NIH 3T3 fibroblasts were transfected with the FBR p75gag-fos gene fusion under the control of the long terminal repeat (LTR) promoter of Finkel-Biskin-Reilly (FBR) murine sarcoma virus and with the gene encoding hygromycin resistance. Several hygromycin-resistant clone isolates, that expressed various levels of p75gag-ros oncoprotein, were analyzed as they displayed properties of transformed cells, such as altered morphology, shorter doubling time, serum-independent growth and foci formation in soft agar. The thermal response of these clones was compared to that of the control cells expressing the hygromycin-resistance gene only. Here, we report that the v-fos-transformed clones displayed an enhanced thermosensitivity which resulted in a reduced tolerance to thermal stress. Heat-treated v-fos-transformed cells displayed a decreased expression and accumulation of the major stress proteins Hsp68 (68-kDa heat-shock protein) and Hsp25 which probably resulted of a reduced accumulation of the corresponding mRNAs. This effect was particularly intense at the level of Hsp25. These alterations in cell survival and stress-protein expression appeared correlated to the level of p75gag-fos. At least for Hsp68, the transcription of this gene was not found altered by v-fos expression suggesting that this oncogene increases the turn-over of Hsp68 mRNA. After the heat-shock treatment, v-fos transformation also reduced the time period during which the constitutively expressed stress protein Hsc70 redistributes inside the nucleus. Since Hsp68 and Hsp25 are molecular chaperones that in vivo protect cells against the deleterious effects of heat shock, it is conceivable that their reduced accumulation and altered cellular distribution following heat shock may contribute, at least in part, to the thermosensitivity of v-fos-transformed NIH 3T3 fibroblasts.

Abbreviations
Hsp

heat-shock or stress protein

FBR

Finkel-Biskin-Reilly

DMEM

Dulbecco's modified Eagle's medium