Do critically short telomeres promote the recombination-dependent pathway?
The original model by Lundblad and Blackburn proposed a stochastic process of recombination events at telomeres, with selection pressure for viability ensuring that there would be a cumulative acquisition of telomeric sequences. A variant of this model is that telomeres become more recombinogenic in the absence of telomerase. A further extension of the model is that recombination occurs in a burst, triggered by critically short telomeres, rather than a succession of cumulative exchanges. Recent studies from several different laboratories suggest that short telomeres are in fact recombinogenic, even before critically shortening or senescence is observed (McEachern and Iyer, 2001; Rizki and Lundblad, 2001). However, additional observations indicate critically short telomeres may also be preferred substrates for at least one type of recombination (Teng et al., 2000). Thus, both variations of this model are likely to contribute to telomerase-independent telomere maintenance. An initial clu
