A programmed site-specific DNA rearrangement in Tetrahymena thermophila requires flanking polypurine tracts
Abstract:
During macronuclear development in ciliates, precise deletion events eliminate thousands of specific DNA segments. Each segment is bounded by a unique pair of short direct repeats, but no other common feature has been reported. To determine the critical cis-acting sequences, we developed an in vivo system for analyzing this process in Tetrahymena. We show that sequences essential for recognition and excision of one such region are located within the 70 bp of DNA flanking either side of it. Three authentic splice sites and one cryptic site are each adjacent to an unusual polypurine tract (5'-A5G5) situated 40-50 bp distal to each terminal repeat. Removal of this tract or substitution of 3 bp within it abolishes splicing to the adjacent site. The normal chromosomal environment and the integrity of the eliminated sequence are not required for its removal. We believe the polypurine tract is a signal essential for excision of this sequence.
Related Concept Videos
Mismatch Repair
The Replisome
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with...
Translesion DNA Polymerases
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
Homologous Recombination
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...
Mismatch Repair
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...


