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Activation of the mas oncogene involves coupling to human alphoid sequences
L J van 't Veer1, M J van der Feltz, C A van den Berg-Bakker
1Department of Clinical Oncology, University Hospital, Leiden, The Netherlands.
Oncogene
|October 1, 1993
Summary
Human ovarian carcinoma DNA activated the mas oncogene in NIH3T3 cells. This activation involved recombination with alpha satellite DNA, leading to oncogene amplification and tumor formation.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- Previous studies demonstrated that NIH3T3 cells transfected with human ovarian carcinoma DNA became tumor-forming due to an activated mas oncogene.
- Rearrangements in the 5'-noncoding region of the mas oncogene were observed in these transfectants compared to the original tumor DNA.
Purpose of the Study:
- To identify the specific DNA sequences involved in the activation of the mas oncogene.
- To elucidate the mechanism by which the mas oncogene is activated in ovarian carcinoma transfectants.
- To investigate the role of alpha satellite DNA in oncogene activation.
Main Methods:
- Transfection of NIH3T3 cells with human ovarian carcinoma DNA.
- Analysis of DNA sequences in tumor-forming transfectants, focusing on rearrangements and newly acquired sequences.
- Co-transfection experiments using cloned alphoid DNA and the mas coding sequence.
- Tumorigenicity assays in nude mice following transfection with specific plasmid constructs.
Main Results:
- In all four tumor-forming transfectants, newly acquired sequences were identified as human centromeric alpha satellite repeat DNA (alphoid DNA).
- Alphoid DNA originated from chromosome three in at least three transfectants.
- Co-transfection with alphoid DNA and the mas coding sequence resulted in NIH3T3 cells with a transformed phenotype, showing amplified mas linked to alphoid DNA.
- Tumorigenic NIH3T3 cells transfected with plasmids containing upstream alphoid sequences and the mas coding sequence exhibited amplified mas sequences (7/7), with alphoid sequences amplified in six tumors.
Conclusions:
- Recombination between the mas oncogene and normal alphoid DNA represents a novel mechanism for oncogene activation.
- This recombination event leads to the amplification of the oncogene, contributing to tumorigenesis.
- Alphoid DNA plays a crucial role in the activation and amplification of the mas oncogene in the context of ovarian carcinoma.