ALTERNATE JUNCTIONS AND MICROHETEROGENEITY OF TLR1, A DEVELOPMENTALLY-REGULATED DNA REARRANGEMENT IN TETRAHYMENA-THERMOPHILA

A large number of developmentally regulated DNA rearrangements occur d uring the development of the macronucleus in Tetrahymena thermophila. Tlr1 is a deletion element which has large inverted repeats near the r earrangement junctions and deletes more than 13 kbp of internal DNA. P revious analysis of caryonidal Lines revealed alternate left junctions for the Tlr1 rearrangement in B strain cells. We show here that C2 st rain Tetrahymena also use alternate rearrangement junctions. We have m apped and sequenced two additional rearrangement variants and find tha t both the left and right junctions can vary over a range of approxima tely 200 bp. We also demonstrate the presence of sequence microheterog eneity in the most commonly found Tlr1 rearrangement product.