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Researchers have discovered a yeast genus that has lost many genes that help other organisms stay free of cancer.
Most organisms possess a variety of genes that repair mutated DNA and help maintain cell division online, slowing the overall mutation rate. Scientists led by Jacob Steenwyk of Vanderbilt University in Tennessee, USA, discovered that members of the Hanseniaspora genus, some of which are commonly found in grapes and grape must, have lost many of these genes with no apparent consequence.
"Because of their importance for ensuring genomic integrity, most of the processes associated with genome maintenance are considered old and largely preserved," say the study authors, published in the journal. PLOS Biology.
"The suppression of many genes associated with the maintenance of DNA results in a dramatic increase in mutation rate and general genome instability."
The researchers analyzed 25 Hanseniaspora genomes of species and found two lineages, one evolving faster than the other. While both had lost a large number of genes that help regulate the cell cycle and preserve the integrity of the genome, the faster-changing lineage had lost the most.
As a result, write the authors, this has gone through a "burst of accelerated evolution, which has resulted in a greater burden of change."
"In genomic terms, Hanseniaspora are the yeast with the least, "says Steenwyk. "They have very small genomes and among the smallest number of genes of any species in the lineage."
Co-author Antonis Rokas said the mutation rate of these yeasts is unprecedented.
"Their cell division seems to be extremely fast but also somewhat erratic – a quantity-rather than quality-oriented approach, so to speak," he says.
The results shed light on an organism's ability to tolerate the absence of genetic material, according to Wayne Crismani of the St. Vincent Medical Research Institute in Melbourne, Australia.
"These yeast species have lost a large selection of some of the most fundamentally important types of genes that are typically used to keep the organism's DNA intact for its survival and spread," he says. he.
Simon Conn, of Flinders University in Australia, says that the loss of only one of these genes can be deadly for yeast and that for humans can be a "hallmark of cancer".
"Some of the most frequently detected mutations in carcinogenic genes, or oncogenes, belong to the DNA repair pathway and the cell cycle control pathways," he adds.
Such mutations can result in a large number of subsequent mutations – that is, an accelerated rate of evolution – and rapid growth of tumors, allowing cancer to survive in the human body and withstanding chemotherapeutic drugs, explains Conn.
"The similarities between growth and mutation patterns observed in this yeast, even over millions of years, and that of human cancers are striking," he says.
According to Conn, the findings could eventually help coordinate new therapies to target DNA repair pathways, while Crismani suggested that they could be useful for increasing the rate of genetic diversity of yeasts intended for manufacturing and cooking, or even plant breeding.
However, the main conclusion of Steenwyk and his colleagues is that, contrary to intuitions, the genus has not been affected by the loss of protective genes.
"We conclude that Hanseniaspora It is an ancient lineage that has diversified and thrives, despite the lack of many genes and cell cycle pathways and genome integrity, which are otherwise highly conserved.
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