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Differential patterns of DNA binding by myc and max proteins
E V Prochownik1, M E VanAntwerp
1Department of Pediatrics, University of Michigan School of Medicine, Ann Arbor 48109.
Summary
The myc and max proteins exhibit distinct DNA binding patterns, with phosphorylation affecting max(long) protein binding. A specific 9-amino acid segment in max regulates DNA sequence recognition.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- The c-myc, N-myc, and L-myc genes are crucial regulators with varied tissue-specific expression.
- Aberrant expression of these myc genes is linked to the development of various cancers.
- The max protein dimerizes with c-myc, facilitating sequence-specific DNA binding.
Purpose of the Study:
- To investigate the DNA binding specificities of different myc proteins, alone and in complex with max.
- To explore the functional impact of max protein isoforms (long and short) on DNA binding.
- To determine the effect of phosphorylation on max protein DNA binding.
Main Methods:
- Recombinant myc and max proteins were synthesized.
- DNA binding assays were performed using six distinct oligonucleotides containing c-myc binding sites.
- Max proteins were incubated in rabbit reticulocyte lysate to assess phosphorylation and its effect on DNA binding.
Main Results:
- Each myc protein displayed unique DNA binding patterns, both independently and when dimerized with max.
- Phosphorylation of max proteins occurred in the reticulocyte lysate.
- Phosphorylation significantly altered DNA binding for max(long) but not for max(short).
Conclusions:
- Myc proteins possess specific DNA binding preferences.
- The 9-amino acid difference between max(long) and max(short) plays a regulatory role in DNA sequence recognition.
- Post-translational modification, such as phosphorylation, adds another layer of control to myc-max complex function.