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A human cellular sequence implicated in trk oncogene activation is DNA damage inducible
R Ben-Ishai1, R Scharf, R Sharon
1Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
Abstract:
Xeroderma pigmentosum cells, which are deficient in the repair of UV light-induced DNA damage, have been used to clone DNA-damage-inducible transcripts in human cells. The cDNA clone designated pC-5 hybridizes on RNA gel blots to a 1-kilobase transcript, which is moderately abundant in nontreated cells and whose synthesis is enhanced in human cells following UV irradiation or treatment with several other DNA-damaging agents. UV-enhanced transcription of C-5 RNA is transient and occurs at lower fluences and to a greater extent in DNA-repair-deficient than in DNA-repair-proficient cells. Southern blot analysis indicates that the C-5 gene belongs to a multigene family. A cDNA clone containing the complete coding sequence of C-5 was isolated. Sequence analysis revealed that it is homologous to a human cellular sequence encoding the amino-terminal activating sequence of the trk-2h chimeric oncogene [Kozma, S. C., Redmond, S. M. S., Xiao-Chang, F., Saurer, S. M., Groner, B. & Hynes, N. E. (1988) EMBO J. 7, 147-154]. The presence of DNA-damage-responsive sequences at the 5' end of a chimeric oncogene could result in enhanced expression of the oncogene in response to carcinogens.
Insights
Researchers identified a DNA-damage-inducible gene (C-5) in human cells. Its expression increases after UV exposure, especially in cells with impaired DNA repair, suggesting a role in carcinogen response.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Xeroderma pigmentosum cells lack DNA repair mechanisms for UV damage.
- Identifying DNA-damage-inducible transcripts is crucial for understanding cellular responses to genotoxic agents.
Purpose of the Study:
- To clone and characterize DNA-damage-inducible transcripts in human cells.
- To investigate the regulation and function of the identified C-5 transcript.
Main Methods:
- Differential screening of cDNA libraries from UV-treated and untreated human cells.
- RNA gel blot analysis to assess transcript abundance and regulation.
- Southern blot analysis to determine gene family size.
- Sequence analysis of the C-5 cDNA clone.
Main Results:
- A 1-kilobase transcript (C-5 RNA) was identified, moderately abundant in normal cells and enhanced by UV irradiation and other DNA-damaging agents.
- UV-enhanced transcription of C-5 RNA was transient and more pronounced in DNA-repair-deficient cells.
- The C-5 gene is part of a multigene family.
- Sequence analysis revealed homology to the amino-terminal activating sequence of the trk-2h chimeric oncogene.
Conclusions:
- The C-5 gene product is a DNA-damage-inducible transcript.
- Its enhanced expression in repair-deficient cells suggests a role in cellular response to DNA damage.
- The homology to an oncogene's activating sequence indicates potential implications in carcinogen-induced oncogenesis.