MutS protein homolog 5 is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
that in humans is encoded by the ''MSH5''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
Function
This gene encodes a member of the mutS family of proteins that are involved in DNA mismatch repair or meiotic recombination processes. This protein is similar to a Saccharomyces cerevisiae protein that participates in meiotic segregation fidelity and crossing-over. This protein forms heterooligomers with another member of this family, mutS homolog 4. Alternative splicing results in four transcript variants encoding three different isoforms.
Mutations
Mice
homozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mo ...
for a null Msh5 mutation (Msh5-/-) are viable but sterile.
In these mice, the
prophase I
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately res ...
stage of
meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately ...
is defective due to the disruption of
chromosome pairing. This meiotic failure leads, in male mice, to diminution of
testicular
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testosteron ...
size, and in female mice, to a complete loss of
ovarian structures.
A genetic investigation was performed to test women with premature ovarian failure for mutations in each of four meiotic genes.
Among 41 women with premature ovarian failure two were found to be
heterozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
...
for a mutation in the MSH5 gene; among 34 fertile women (controls) no mutations were found in the four tested genes.
These findings in mouse and human indicate that the MSH5 protein plays an important role in meiotic recombination.
In the worm ''
Caenorhabditis elegans
''Caenorhabditis elegans'' () is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek ''caeno-'' (recent), ''rhabditis'' (r ...
'', the MSH5 protein is required during meiosis both for normal spontaneous and for gamma-irradiation induced crossover recombination and chiasma formation.
Meiotic recombination is often initiated by double strand breaks. MSH5 mutants retain the competence to repair DNA double-strand breaks that are present during meiosis, but they accomplish this repair in a way that does not lead to crossovers between homologous chromosomes.
The known mechanism of non-crossover recombinational repair is called synthesis dependent strand annealing (see
homologous recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
). MSH5 thus appears to be employed in directing the
recombinational repair of some double-strand breaks towards the cross over option rather than the non-cross over option.
Interactions
MSH5 has been shown to
interact
Advocates for Informed Choice, doing business as, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex trai ...
with
MSH4.
References
Further reading
*
*
*
*
*
*
*
*
*
*
*
*
*
{{refend