DEVELOPMENTALLY EXCISED DNA-SEQUENCES IN EUPLOTES-CRASSUS CAPABLE OF FORMING G QUARTETS

Tens of thousands of DNA segments are eliminated by DNA breakage and r ejoining events during the formation of a new macronucleus in the hypo trichous ciliated protozoan Euplotes crassus. This study presents evid ence for a class of eliminated sequences referred to as telomeric-repe at-like internal eliminated sequences (TelIESs). TelIESs are shorter ( <50 bp) than most previously characterized IESs and their DNA sequence s resemble the telomeric repeat sequences of the organism. The TelIESs are excised during the developmental period of chromosome fragmentati on/telomere addition, which is later than previously characterized IES s. Additional studies demonstrate that oligonucleotides representing t he TelIESs are, like telomeric repeats, capable of forming G-quartet s tructures in vitro.