DNA replication licensing factor MCM8 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, respo ...

that in humans is encoded by the ''MCM8''

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 ba ...

. The protein encoded by this gene is one of the highly conserved mini-chromosome maintenance proteins (MCM) that are essential for the initiation of eukaryotic genome replication. The hexameric protein complex formed by the MCM proteins is a key component of the pre-replication complex (pre_RC) and may be involved in the formation of replication forks and in the recruitment of other DNA replication related proteins. This protein contains the central domain that is conserved among the MCM proteins. This protein has been shown to co-immunoprecipitate with MCM4, 6 and 7, which suggests that it may interact with other MCM proteins and play a role in DNA replication. Alternatively spliced transcript variants encoding distinct isoforms have been described.

DNA repair

MCM8-deficient mice are defective in

gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic d ...

and display

genome instability Genome instability (also genetic instability or genomic instability) refers to a high frequency of mutations within the genome of a cellular lineage. These mutations can include changes in nucleic acid sequences, chromosomal rearrangements or aneu ...

due to impaired

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 ...

. Male MCM8 (-/-) mice are sterile because

spermatocyte Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and ...

s are blocked in

meiotic 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 ...

prophase I. Female MCM8(-/-) mice have arrested primary follicles and frequently develop ovarian tumors. MCM8 protein forms a complex with MCM9. In the plant ''

Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter a ...

'', MCM8 is required for a pathway of

DNA double-strand break repair. It was proposed that MCM8 is involved with RAD51 in a backup pathway that repairs meiotic double-strand breaks without yielding crossovers when the major recombination pathway, which relies on

DMC1 Meiotic recombination protein DMC1/LIM15 homolog is a protein that in humans is encoded by the ''DMC1'' gene. Meiotic recombination protein Dmc1 is a homolog of the bacterial strand exchange protein RecA. Dmc1 plays the central role in homologous ...

, fails.

MCM8 forms a complex with MCM9 that is required for DNA resection by the MRN complex (

MRE11 Double-strand break repair protein MRE11 is an enzyme that in humans is encoded by the ''MRE11'' gene. The gene has been designated ''MRE11A'' to distinguish it from the pseudogene ''MRE11B'' that is nowadays named ''MRE11P1''. Function This ge ...

RAD50 DNA repair protein RAD50, also known as RAD50, is a protein that in humans is encoded by the ''RAD50'' gene. Function The protein encoded by this gene is highly similar to ''Saccharomyces cerevisiae'' Rad50, a protein involved in DNA double- ...

NBS1 Nibrin, also known as NBN or NBS1, is a protein which in humans is encoded by the ''NBN'' gene. Function Nibrin is a protein associated with the repair of double strand breaks (DSBs) which pose serious damage to a genome. It is a 754 amino ac ...

) at double strand breaks to generate single-stranded DNA ends. The formation of single-strand ends is an early step in

(see Figure). MCM8/MCM9 interacts with MRN and is required for the nuclease action and stable association of MRN with double-strand breaks. In humans, an MCM8 mutation can give rise to premature ovarian failure, as well as

chromosomal instability Chromosomal instability (CIN) is a type of genome instability, genomic instability in which chromosomes are unstable, such that either whole chromosomes or parts of chromosomes are duplicated or deleted. More specifically, CIN refers to the increas ...

DNA repair

See also

References

Further reading