Impact of ionizing radiation on the life cycle of Saccharomyces cerevisiae Ty1 retrotransposon

Abstract

Ty1 elements, LTR-retrotransposons of Saccharomyces cerevisiae, are known to be activated by genetic and environmental stress. Several DNA-damaging agents have been shown to increase both Ty1 transcription and retrotransposition. To explore further the relationship between Ty1 mobility and DNA damage, we have studied the impact of ionizing radiation at different steps of the Ty1 life cycle. We have shown that Ty1 transposition is strongly activated by γ -irradiation and we have analysed its effect on Ty1 transcription, TyA1 protein and Ty1 cDNA levels. The activation of transposition rises with increasing doses of γ -rays and is stronger for Ty1 elements than for the related Ty2 elements. Ty1 RNA levels are markedly elevated upon irradiation; however, no significant increase of TyA1 protein was detected as measured by TYA1-lacZ fusions and by Western blot. A moderate increase in Ty1 cDNA levels was also observed, indicating that ionizing radiation can induce the synthesis of Ty1 cDNA. In diploid cells and ste12 mutants, where both Ty1 transcription and transposition are repressed, γ -irradiation is able to activate Ty1 transposition and increases Ty1 RNA levels. These results suggest the existence of a specific regulatory pathway involved in Ty1 response to the γ -irradiation that would be independent of Ste12 and mating-type factors. Our findings also indicate that ionizing radiation acts on several steps of the Ty1 life cycle.

SREBP Controls Oxygen-Dependent Mobilization of Retrotransposons in Fission Yeast

“…Retrotransposon transcription and subsequent transposition are upregulated by different environmental conditions and stresses. Ionizing radiation, DNA damage, mating pheromone, and nutrient limitation activate S. cerevisiae Ty elements [10,14,15]; heat and sodium azide induce Drosophila copia elements [16]; and wounding, biotic elicitors, and pathogen attack activate Tnt1 in the Solanaceae plant family [17]. One well-understood regulatory mechanism involves the transcriptional activators Ste12 and Tec1, which regulate S. cerevisiae Ty1 elements in response to mating pheromones, nitrogen starvation, and invasive growth signals [18][19][20].…”

Remodeling Yeast Gene Transcription by Activating the Ty1 Long Terminal Repeat Retrotransposon under Severe Adenine Deficiency

“…Different kinds of environmental stress, such as ionizing radiation, DNA damage, nitrogen starvation, and severe adenine starvation, activate Ty1 transcription and mobility (11,45,49,54,56,61,64). Studies to understand the impact of Ty1 insertions on adjacent gene transcription and to decipher the mechanisms of Ty1 activation by stress have provided several clues on Ty1 promoter structure and on the transcription factors involved in Ty1 transcription.…”

Preferential Epigenetic Suppression of the Autonomous MusD over the Nonautonomous ETn Mouse Retrotransposons

“…It has been shown that elevated expression of LTR retrotransposons can lead to their genomic expansion via retrotransposition (12,19,20,45,53). We suggest that, in some cases, the abundance of transcripts may be a limiting factor in the retrotransposition process.…”

“…However, the preponderance of ETnII-induced germ line mutations implies otherwise. Since transcription rate has been shown to correlate with retrotransposition efficiency (12,19,20,45,53), we hypothesize that the current skewing of retrotranspositional events to the ETnII subfamily is due to the much higher number of ETnII than MusD transcripts available for copackaging with MusD-encoded proteins.…”