Induction of global stress response in Saccharomyces cerevisiae cells lacking telomerase

Cellular senescence is a major intermediate step from healthy cells toward tumor cells. By using mi-croarrays that simultaneously examine the transcription levels of 6, 200 Saccharomyces cerevisiae genes, we show that 45 gene transcript levels are increased and 11 are decreased after exposure to telomere shortening and cellular senescence in a telomerase-deficient mutant. About half of the genes that showed increased expression were found induced under stress, consistent with the notion that critical short telomeres cause stress to cells. Surprisingly, the expression level of telomere recombination genes was not altered suggesting that even though recombination is a means to rescue critically short telomeres, its machinery was not controlled by telomere shortening. The expression of telomere-proximal genes was also analyzed. The possibility of induction of a program to cope with cellular senescence and active telomere-telomere recombination is discussed.