FIG 2.

I-SceI telomere formation system. (A) The I-SceI endonuclease was expressed from the TetR-controlled CaMV35S promoter in a cassette that also expresses TetR. The addition of ahTET induces I-SceI expression, which then cuts at sites introduced into the genome (red triangles). (B) The 48-bp prototelomere contains the ura4⁺ gene followed by 48 bp of telomere repeats (black triangles) and the hygromycin resistance marker (hph⁺), while the 0-bp prototelomere control lacks the telomere repeats. Both cassettes were inserted into the unique DNA 3′ of the gal1⁺ gene. The S. pombe endogenous telomere repeat tracts are indicated by gray triangles.