Related Experiment Videos
The phage Mu transpososome core: DNA requirements for assembly and function
H Savilahti1, P A Rice, K Mizuuchi
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
The EMBO Journal
|October 2, 1995
Summary
Phage Mu transposition involves protein-DNA complexes called transpososomes. DNA flanking sequences and divalent cations influence transpososome stability and activity, revealing insights into transposition mechanisms.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Phage Mu transpositional recombination involves two key steps: donor DNA cleavage and strand transfer.
- These reactions occur within higher-order protein-DNA complexes known as transpososomes, primarily composed of a MuA transposase tetramer bound to Mu genome ends.
Purpose of the Study:
- To investigate the DNA requirements for transpososome assembly and the stability and activity of these complexes under specific conditions.
- To elucidate the role of flanking DNA sequences and divalent cations in Mu transposition.
Main Methods:
- Characterization of transpososome formation using only MuA transposase and short DNA fragments.
- Analysis of DNA requirements, including substrate nicking, flanking DNA length, and strand complementarity.
- Investigation of divalent cation requirements (Mg2+ and Ca2+) for DNA cleavage and strand transfer.
Main Results:
- Transpososome assembly can occur without cofactors under certain conditions, requiring only MuA and specific DNA substrates.
- Divalent cations are not always essential for stable complex assembly if the substrate is nicked, has very short flanking DNA, or non-complementary strands.
- Transpososome stability critically depends on a single nucleotide beyond the Mu genome end on the non-cut strand.
- Donor DNA cleavage requires at least two flanking nucleotides on the cleaved strand, and the flanking DNA helix is destabilized.
- Donor cleavage necessitates Mg2+, while strand transfer can proceed with Ca2+, indicating distinct active site conformations.
Conclusions:
- The study defines critical DNA sequence and structural requirements for stable transpososome formation and function.
- The findings suggest that DNA distortion near the active site is involved in donor cleavage.
- The differential cation requirements for cleavage and transfer imply distinct conformational states of the MuA active site during transposition.