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MSH4 acts in conjunction with MLH1 during mammalian meiosis
S Santucci-Darmanin1, D Walpita, F Lespinasse
1Laboratoire de Neurobiologie Cellulaire, UMR CNRS/UNSA 6549, Faculté de Médecine, 06107 Nice cédex 2, France.
Abstract:
MSH4 is a meiosis-specific MutS homolog. In yeast, it is required for reciprocal recombination and proper segregation of homologous chromosomes at meiosis I. MLH1 (MutL homolog 1) facilitates both mismatch repair and crossing over during meiosis in yeast. Germ-line mutations in the MLH1 human gene are responsible for hereditary nonpolyposis cancer, but the analysis of MLH1-deficient mice has revealed that MLH1 is also required for reciprocal recombination in mammals. Here we show that hMSH4 interacts with hMLH1. The two proteins are coimmunoprecipitated regardless of the presence of DNA or ATP, suggesting that the interaction does not require the binding of MSH4 to DNA. The domain of hMSH4 responsible for the interaction is in the amino-terminal part of the protein whereas the region that contains the ATP binding site and helix-turn-helix motif does not bind to hMLH1. Immunolocalization analysis shows that MSH4 is present at sites along the synaptonemal complex as soon as homologous chromosomes synapse. The number of MSH4 foci decreases gradually as pachynema progresses. During this transition, MLH1 foci begin to appear and colocalize with MSH4. These results suggest that MSH4 is first required for chromosome synapsis and that this MutS homologue is involved later with MLH1 in meiotic reciprocal recombination.
Insights
Human MSH4 (MutS homolog 4) interacts with human MLH1 (MutL homolog 1), suggesting a role in meiotic recombination. This interaction is crucial for homologous chromosome pairing and segregation during meiosis.
Area of Science:
- Genetics
- Molecular Biology
- Cell Biology
Background:
- MSH4 is a meiosis-specific MutS homolog essential for homologous chromosome segregation in yeast.
- MLH1 is involved in DNA mismatch repair and crossing over, with germline mutations linked to hereditary nonpolyposis cancer.
- MLH1 is also required for reciprocal recombination in mammals.
Purpose of the Study:
- To investigate the interaction between human MSH4 (hMSH4) and human MLH1 (hMLH1).
- To elucidate the roles of hMSH4 and hMLH1 in mammalian meiosis, particularly in chromosome synapsis and recombination.
Main Methods:
- Coimmunoprecipitation assays to detect protein-protein interactions.
- Analysis of protein domains involved in binding.
- Immunolocalization studies to determine the spatial and temporal localization of MSH4 and MLH1 during meiosis.
Main Results:
- hMSH4 and hMLH1 were found to interact and could be coimmunoprecipitated.
- The interaction between hMSH4 and hMLH1 does not require DNA or ATP binding.
- MSH4 localizes to the synaptonemal complex early in meiosis, followed by MLH1, with MSH4 and MLH1 foci colocalizing later.
- The N-terminal domain of hMSH4 mediates the interaction with hMLH1.
Conclusions:
- hMSH4 is initially involved in homologous chromosome synapsis.
- hMSH4 collaborates with hMLH1 in meiotic reciprocal recombination.
- The findings provide insights into the molecular mechanisms of meiotic recombination in mammals.