In Schizosaccharomyces pombe the RNAi machinery and proteins mediating 
heterochromatin formation regulate the transcription of non-coding centromeric 
repeats. These repeats share a high sequence similarity with telomere-linked 
helicase (tlh) genes, implying an ancestral relationship between the two types 
of elements and suggesting that transcription of the tlh genes might be 
regulated by the same factors as centromeric repeats. Indeed, we found that 
mutants lacking the histone methyltransferase Clr4, the Pcu4 cullin, Clr7 or 
Clr8, accumulate high levels of tlh forward and reverse transcripts. Mutations 
and conditions perturbing histone acetylation had similar effects further 
demonstrating that the tlh genes are normally repressed by heterochromatin. In 
contrast, mutations in the RNAi factors Dcr1, Ago1 or Rdp1 led only to a modest 
derepression of the tlh genes indicating an alternate pathway recruits 
heterochromatin components to telomeres. The telomere-binding protein Taz1 might 
be part of such a redundant pathway, tlh transcripts being present at low levels 
in Deltataz1 mutants and at higher levels in Deltataz1 Deltadcr1 double mutants. 
Surprisingly, the chromodomain protein Chp1, a component of the Ago1-containing 
RITS complex, contributes more to tlh repression than Ago1, indicating the 
repressive effects of Chp1 are partially independent of RITS. The tlh genes are 
found in the subtelomeric regions of several other fungi raising the intriguing 
possibility of conserved regulation and function.