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Characterization and chromosomal localization of the human proto-oncogene BMI-1
M J Alkema1, J Wiegant, A K Raap
1Division of Molecular Genetics, University of Amsterdam, The Netherlands Cancer Institute.
Abstract:
The proto-oncogene bmi-1 is frequently activated by Moloney murine leukemia proviral insertions in E mu-myc transgenic mice1,2. Using a mouse bmi-1 cDNA probe a transcript of 3.3 kb was detected on Northern blots of human Burkitt's lymphoma cell lines. We have isolated and sequenced cDNA clones from a human erythroleukemia cell line (K562) derived cDNA library, using different mouse bmi-1 cDNA fragments as a probe. Analysis of genomic BMI-1 sequences reveals a gene structure which is very similar to that of the mouse, consisting of at least 10 exons. The human cDNA is 3203 bp in length and shows 86% identity to the mouse nucleotide sequence. The open reading frame encodes a protein of 326 amino acids which shares 98% identity to the amino acid sequence of mouse bmi-1 protein. In vitro translation experiments show that human cDNA derived RNA translates into a protein with a mobility of 44-46 kD on SDS polyacrylamide gels. Fluorescence in situ hybridization (FISH) on metaphase chromosome spreads located the human BMI-1 gene to the short arm of chromosome 10 (10p13), a region known to be involved in translocations in various leukemias.
Insights
The proto-oncogene BMI-1, crucial in certain leukemias, was identified in human cells. Its gene structure closely resembles the mouse version, with high protein sequence identity.
Area of Science:
- Molecular Biology
- Genetics
- Oncology
Background:
- The proto-oncogene BMI-1 is implicated in leukemogenesis, often activated by viral insertions in mouse models.
- BMI-1 plays a role in cell proliferation and has been observed in human Burkitt's lymphoma cell lines.
Purpose of the Study:
- To isolate and characterize the human BMI-1 gene and its protein.
- To determine the genomic structure and chromosomal location of human BMI-1.
Main Methods:
- Screening a human erythroleukemia (K562) cDNA library using mouse BMI-1 cDNA probes.
- Sequencing of human BMI-1 cDNA clones.
- Analysis of genomic sequences for gene structure.
- In vitro translation of human BMI-1 cDNA.
- Fluorescence in situ hybridization (FISH) for gene localization.
Main Results:
- Human BMI-1 cDNA of 3203 bp was isolated, showing 86% nucleotide identity to mouse BMI-1.
- The gene structure, with at least 10 exons, is highly similar to mouse BMI-1.
- The encoded protein (326 amino acids) shares 98% identity with mouse BMI-1.
- FISH mapped the human BMI-1 gene to chromosome 10p13, a region associated with leukemia translocations.
Conclusions:
- Human BMI-1 is a highly conserved gene with structural and functional similarities to its mouse counterpart.
- The localization of BMI-1 to 10p13 provides a genetic marker potentially involved in leukemic translocations.