Yeast study identifies the precise mechanism behind telomeric gene amplification

Researchers at the University of Washington and collaborating institutions, led by Bonita J. Brewer, M. K. Raghuraman, and Maitreya J. Dunham, have published findings in PLOS Genetics describing the mechanism by which the SUL1 gene and Y' telomeric elements become amplified in Saccharomyces cerevisiae grown under long-term sulfate limitation.

Gene amplification — the acquisition of extra gene copies — is a driver of evolutionary adaptation and is also implicated in oncogene amplification in human cancers. Using chemostat competition experiments and detailed molecular characterisation, the team shows that amplicons at the SUL1 locus are generated by microhomology-mediated break-induced replication (MMBIR) acting in cis — meaning the replication template is on the same chromosome, rather than involving an inter-chromosomal interaction. This distinguishes the mechanism from some previously proposed models.

The study documents the architecture of the resulting amplicons, showing that MMBIR produces tandem duplications whose boundaries correspond to short regions of microhomology, consistent with template-switching during repair synthesis. The work positions telomeric sequences as hotspots for this class of amplification event, in part because of the repetitive Y' elements that flank subtelomeric genes.

For researchers working on genome instability, cancer genomics, or the molecular archaeology of structural variants, the study provides a tractable model system and mechanistic detail that may inform interpretation of analogous amplification events in human cells.