Developmentally regulated telomere addition inTetrahymena thermophila

Abstract

To investigate the developmentally programmed telomere addition that accompanies chromosome fragmentation during macronuclear differentiation in Tetrahymena thermophila . five representative telomeric regions from the macronucleus were cloned and characterized in detail. The sequences adjacent to the telomeric (C ₄ A ₂ :T ₂ G ₄ ) repeats on these five macronuclear ends had no significant sequence homology or shared secondary structure. Two developmentally independent examples of one macronuclear telomere had a 5 base pair difference in the position of the junction between the telomeric repeats and the adjacent sequences. A telomere-adjacent sequence, in the form of a synthetic oligonucleotide, was unable to prime the addition of telomeric repeats in vitro . The implications of these results for the mechanisms underlying developmentally programmed chromosome fragmentation and telomere addition in Tetrahymena are discussed.