Suppression of v-sis-dependent transformation by the transcription factor, Egr-1

Oncogene. 1994 May;9(5):1367-77.

Abstract

The transcription factor Egr-1, stimulates the activity of a number of genes and inhibits other genes, by binding to the sequence GCGGGGGCG in 5' enhancer regions. However, the functions of Egr-1 are obscure in spite of its rather ubiquitous expression. Egr-1 may play a role in proliferation in mitogen-stimulated cells but its expression is also correlated with the differentiated state in teratocarcinoma cells. The constitutive expression of Egr-1 appears to have little effect on the growth rate of normal immortalized cell-lines. We show that in NIH3T3 cells that are conditionally transformed by the expression of v-six, the presence of Egr-1 is inhibitory to the production of transformed colonies (foci) and to growth in soft agar. In addition, the first appearance of tumors in nu/nu mice is delayed in tumorigenicity tests with cells that over-express Egr-1 and tumor growth is suppressed compared to control cells. We used a series of fragments of Egr-1 cloned into expression vectors to show that not only full length, but also truncated Egr-1 fragments inhibit colony formation. Using deletion mutants, we observed that this inhibitory activity is dependent on the presence of the DNA-binding 'zinc-finger' region. Wilm's tumor protein, WT1, (known to be a tumor suppressor gene) that exhibits the same DNA binding activity is also inhibitory. In contrast, colony formation is stimulated by an Egr-1 antisense RNA-expressing plasmid, since colonies grow rapidly and the colony-forming frequency is higher than in the presence of v-sis alone. We conclude that proteins containing the Egr-1 'zinc-finger' domain can bind to the regulatory regions of one or more genes that are required for the transformation of fibroblasts by v-sis thus inhibiting transformation. One function for Egr-1 implied by these results is the restraint of transformed growth in mitogen-stimulated cells.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells / pathology
  • Animals
  • Base Sequence
  • Cell Adhesion
  • Cell Division
  • Cell Transformation, Neoplastic* / drug effects
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / physiology*
  • Early Growth Response Protein 1
  • Immediate-Early Proteins*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Molecular Sequence Data
  • Mutation
  • Neoplasm Transplantation
  • Oncogene Proteins v-sis
  • RNA, Antisense / metabolism
  • RNA, Antisense / physiology
  • Retroviridae Proteins, Oncogenic / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology*
  • Tumor Stem Cell Assay
  • Zinc Fingers

Substances

  • DNA-Binding Proteins
  • Early Growth Response Protein 1
  • Egr1 protein, mouse
  • Immediate-Early Proteins
  • Oncogene Proteins v-sis
  • RNA, Antisense
  • Retroviridae Proteins, Oncogenic
  • Transcription Factors