Spo11: Difference between revisions

Genetic exchange between two DNA molecules by [[homologous recombination]] begins with a break in both strands of DNA—called a double-strand break—and recombination is started by an [[endonuclease]] enzyme that cuts the DNA molecule that "receives" the exchanged DNA. In [[meiosis]] the enzyme is SPO11, which is related to DNA [[topoisomerase]]s. Topoisomerases change DNA by transiently breaking one or both strands, passing the unbroken DNA strand or strands through the break and repairing the break; the broken ends of the DNA are covalently linked to topoisomerase. SPO11 is similarly attached to the DNA when it forms double-strand breaks during meiosis.<ref name="isbn0-7637-7992-X">{{cite book |title=Lewin's Genes X |edition=10th |publisher=Jones and Bartlett Publishers, Inc. |location= |year=2011 |origyear= |pages=353–354 |isbn=978-0-7637-7992-4 |oclc= |doi= |url= |access-date=}}</ref>

In the budding yeast ''Sacharomyces cerevisiae'', the meiotic defects in recombination and chromosome disjunction of ''spo11'' mutants are alleviated by X-irradiation.<ref name="pmid8514137">{{cite journal | vauthors = Thorne LW, Byers B | title = Stage-specific effects of X-irradiation on yeast meiosis | journal = Genetics | volume = 134 | issue = 1 | pages = 29–42 | date = May 1993 | pmid = 8514137 | pmc = 1205431 | doi = }}</ref> This finding indicates that X-ray induced DNA damages can initiate crossover recombination leading to proper disjunction independently of SPO11.

The most recent common ancestor of the social [[amoeba]] genera ''[[Dictyostelium]]'', ''[[Polysphondylium]]'' and ''[[Acytostelium]]'', appears to have lacked the ''Spo11'' gene.<ref name=Bloomfield>{{cite journal | vauthors = Bloomfield G | title = Atypical ploidy cycles, Spo11, and the evolution of meiosis | journal = Seminars in Cell & Developmental Biology | volume = 54 | issue = | pages = 158–64 | date = June 2016 | pmid = 26811992 | doi = 10.1016/j.semcdb.2016.01.026 | url = https://zenodo.org/record/889469 }}</ref><ref name="pmid18663385">{{cite journal | vauthors = Malik SB, Pightling AW, Stefaniak LM, Schurko AM, Logsdon JM | title = An expanded inventory of conserved meiotic genes provides evidence for sex in Trichomonas vaginalis | journal = PLOS ONE | volume = 3 | issue = 8 | pages = e2879 | date = August 2007 | pmid = 18663385 | pmc = 2488364 | doi = 10.1371/journal.pone.0002879 }}</ref> Such an ancestor likely lived several hundred million years ago.<ref name="pmid24040233">{{cite journal | vauthors = Fiz-Palacios O, Romeralo M, Ahmadzadeh A, Weststrand S, Ahlberg PE, Baldauf S | title = Did terrestrial diversification of amoebas (amoebozoa) occur in synchrony with land plants? | journal = PLOS ONE | volume = 8 | issue = 9 | pages = e74374 | year = 2013 | pmid = 24040233 | pmc = 3770592 | doi = 10.1371/journal.pone.0074374 | bibcode = 2013PLoSO...874374F }}</ref> ''[[Dictyostelium discoideum]]'' and ''[[Polysphondylium pallidum]]'' are both capable of [[meiosis|meiotic]] [[sexual reproduction]] (see ''[[Dictyostelium discoideum#Sexual reproduction|''D. discoideum'' sexual reproduction]]'' and ''[[Polysphondylium pallidum#Sexual reproduction|''P. pallidum'' sexual reproduction]]''). Bloomfield<ref name=Bloomfield /> speculated that dormant cells in the soil might be exposed to many kinds of stress, such as desiccation or radiation, that could induce spontaneous [[DNA damage (naturally occurring)|DNA damage]]. Such damage would make the induction of double-strand breaks by Spo11 redundant for the initiation of [[genetic recombination|recombination]] during meiosis, and thus explain its absence in this group.