Alpha3, a transposable element that promotes host sexual reproduction.

Area of Science:

• * Molecular Biology
• * Genetics
• * Evolutionary Biology

Background:

• * Theoretical models suggest selfish DNA requires host sexual reproduction for persistence.
• * Transposons that induce sex could enhance their own spread within a population.

Purpose of the Study:

• * To investigate the role of a transposase-homologous protein, alpha3, in mating type switching in *Kluyveromyces lactis*.
• * To provide empirical evidence for selfish DNA promoting host sexual reproduction.

Main Methods:

• * Mutational analysis of the alpha3 protein and its flanking sequences.
• * Examination of DNA circle formation during mating type switching.
• * Investigation of the DNA-binding protein Mating type switch 1 (Mts1) and its role.
• * Analysis of DNA double-strand breaks (DSBs) in specific yeast mutants.

Main Results:

• * The alpha3 protein, homologous to transposases, is essential for mating type switching in *K. lactis*.
• * Alpha3 mobilization from the genome, forming a DNA circle, is coupled to the switching process.
• * Mating type switch 1 (Mts1) is required, with its expression regulated by ploidy and nutrients.
• * Mating type-specific DSBs induce the mating type switch.

Conclusions:

• * Selfish DNA elements can actively promote host sexual reproduction.
• * The alpha3 transposon mediates mating type switching in yeast, facilitating its own evolutionary persistence.
• * This mechanism highlights a co-evolutionary dynamic between selfish genetic elements and host reproductive strategies.