Sea3 impacts senescence progression and the formation of survivors in the absence of telomerase. (A) Proposed pathway indicating that SEACAT, which contains Sea2, Sea3, and Sea4, acts as a negative regulator of Iml1 complex/SEACIT, which contains Iml1, Npr2, and Npr3. The Iml1 complex/SEACIT functions as a negative regulator of TORC1 signaling, which regulates a variety of downstream targets. (B) Southern blot of XhoI-digested genomic DNA isolated from wild-type and haploid SEA complex gene deletion mutants were probed with a telomere repeat specific probe. Approximately two thirds of wild-type telomeres, which contain Y´ elements in the subtelomeric region, give rise to a 1.2-kb terminal restriction fragment upon XhoI digestion. The restriction fragments of greater length derive, in part, from individual telomeres that lack a Y´ element. (C) Liquid culture senescence progression assays of tlc1∆ and sea3∆ tlc1∆ haploids obtained from sporulation and microdissection of a sea3Δ/SEA3 tlc1Δ/TLC1 diploid. Blue lines indicate growth curves of individual tlc1Δ spores (n = 7), and red lines indicate growth curves of individual sea3Δ tlc1Δ spores (n = 5). (D) As in (B) except genomic DNA was isolated daily from samples in the liquid senescence progression assay (C). Arrows indicate the emergence of Type II survivors, which acquired a more heterogeneous banding pattern.