Advancements in genome sequencing support hypothesise that transposons make up large parts of genomes. Numerous examples exist that also support stress induced activation of transposons (Morish et al 2007). Little is known though, how signals induced by stress relay to transposons.
Importantly advancements in position selection for insertions by transposons have been made through work on Ty elements in Saccharomyces cerevisiae. Ty elements are long terminal repeats (LTR) retrotransposons. In Ty5 exists the preference to bind 2 ways.
Firstly, Ty5 can intergrate into heterochromatin, which is tightly packed DNA with limited transcription. When the intergrase of Ty5 is phosphorlated, the interaction between that intergrase and Sir4p, which is an intergral piece of heterochromatin, is stabilized. Experiments have been shown that for the Ty5 to bind the DNA needs to be secured to the Sir4p.
the second binding preference of Ty5 is that it can intergrate into the genome to protect it. When Sir4p is bound to LexA the Ty5 intergrase binds to the lexA protect the gemone. Along with protetion it is possibly to insure that copies of Ty5 are always available.
The possibilty that Ty5 can bind 2 ways possibly means other retrotransposons may do also. It as been proposed therefore from this evidence that the genome may use transposons to rearrange itself when stress is applied.
by Charlie Brunello 41189757
References.
Ebina, H; Levin, H.L. (2007) Stress management: How Cells Take Control of Their Transposons. Cell Press p180-181
Morrish, T.A. Garcia-Peez, J.L., Stamato, T.D., Taccioli, G.E., Sekiguchi, J., and Moran, J.V. (2007) Endonuclease-independent LINE-1 retrotransposition at mammalian telomeres Nature 446, 208-212
