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Human MutS homologue MSH4 physically interacts with von Hippel-Lindau tumor suppressor-binding protein 1
Chengtao Her1, Xiling Wu, Michael D Griswold
1School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99164-4660, USA. cher@wsu.edu
Abstract:
Increasing evidence indicated that the protein factors involved in DNA mismatch repair (MMR) possess meiotic functions beyond the scope of DNA mismatch correction. The important roles of MMR components in meiotic processes have been highlighted by the recent identification of two additional members of the mammalian MutS homologs, MSH4 and MSH5. Mammalian MSH4 and MSH5 proteins form a heterodimeric complex and play an important role in the meiotic processes. As a step forward to the understanding of the molecular mechanisms underlying the roles of these two mammalian MutS homologues, here we have identified von Hippel-Lindau (VHL) tumor suppressor-binding protein 1 (VBP1) as an interacting protein partner for human MSH4 (hMSH4). In addition, we have characterized a hMSH4 splicing variant (hMSH4sv) encoding a truncated form of hMSH4. The protein encoded by hMSH4sv was unable to interact with hMSH5, but it retained the capacity to interact with VBP1. It is conceivable that hMSH4 and hMSH4sv can carry out different but overlapping functions by differential protein interactions, and, therefore, hMSH4sv might represent a separation-of-function alternative form of the hMSH4 protein. hMSH4 and VBP1 proteins were colocalized in mammalian cells. Three-hybrid analysis suggested that VBP1 could compete with hMSH5 for the binding of hMSH4. Thus, hMSH4 may be involved in diverse cellular processes through interaction with different protein partners, and the levels of VBP1 protein expression in cells could potentially affect the availability of the hMSH4-hMSH5 hetero-complex.
Insights
DNA mismatch repair proteins MSH4 and MSH5 have meiotic roles. Researchers found MSH4 interacts with VBP1, and a variant, hMSH4sv, interacts with VBP1 but not MSH5, suggesting distinct functions.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- DNA mismatch repair (MMR) proteins, including MutS homologs (MSH), have functions beyond DNA repair, particularly in meiosis.
- MSH4 and MSH5 are mammalian MutS homologs that form a heterodimeric complex crucial for meiotic processes.
Purpose of the Study:
- To elucidate the molecular mechanisms of MSH4 and MSH5 in meiosis.
- To identify novel interaction partners of human MSH4 (hMSH4).
- To characterize a novel splicing variant of hMSH4 (hMSH4sv) and its functional implications.
Main Methods:
- Yeast three-hybrid analysis to identify protein interaction partners.
- Characterization of a human MSH4 splicing variant (hMSH4sv).
- Immunofluorescence to assess protein colocalization in mammalian cells.
Main Results:
- Von Hippel-Lindau (VHL) tumor suppressor-binding protein 1 (VBP1) was identified as an interacting partner of hMSH4.
- A truncated splicing variant, hMSH4sv, interacts with VBP1 but not with MSH5.
- hMSH4 and VBP1 colocalize in mammalian cells, and VBP1 competes with MSH5 for hMSH4 binding.
Conclusions:
- hMSH4 interacts with VBP1, suggesting roles in diverse cellular processes beyond its interaction with MSH5.
- The hMSH4sv variant may represent a separation-of-function alternative, mediating distinct cellular roles through differential protein interactions.
- VBP1 levels can influence the availability of the hMSH4-MSH5 complex, highlighting a regulatory mechanism in meiotic processes.