The Tetrahymena p80/p95 complex is required for proper telomere length maintenance and micronuclear genome stability.

The telomerase enzyme adds simple sequence repeats to chromosome ends. Telomerases share two essential subunits, telomerase RNA and telomerase reverse transcriptase, that associate with species-specific proteins of predominantly unknown functions. The Tetrahymena p80/p95 complex can coimmunopurify active telomerase from cell extract, and recombinant p80/p95 can interact directly with telomerase RNA and single-stranded telomeric DNA in vitro. Here, we test the functions of p80/p95 in vivo. Surprisingly, telomerase RNA accumulation and telomerase activity in cell extract are unaffected by loss of the genes encoding p80/p95. However, in the absence of p80/p95, telomeres become elongated in both macronuclei and micronuclei. Micronuclear chromosome maintenance is also compromised. These findings suggest that p80/p95 functions to maintain appropriate telomere length and micronuclear genomic stability but does so in a manner different than previously anticipated.