A METHYLATED HUMAN 9-KB REPETITIVE SEQUENCE ON ACROCENTRIC CHROMOSOMES IS HOMOLOGOUS TO A SUBTELOMERIC REPEAT IN CHIMPANZEES

We have implemented an approach for the detection of DNA alterations i n cancer by means of computerized analysis of end-labeled genomic frag ments, separated in two dimensions. Analysis of two-dimensional patter ns of neuroblastoma tumors, prepared by first digesting DNA with the m ethylation-sensitive restriction enzyme Not I, yielded a multicopy fra gment which was detected in some tumor patterns but not in normal cont rols, Cloning and sequencing of the fragment, isolated from two-dimens ional gels, yielded a sequence with a strong homology to a subtelomeri c sequence in chimpanzees and which was previously reported to be unde tectable in humans. Fluorescence in situ hybridization indicated the o ccurrence of this sequence in normal tissue, for the most part in the satellite regions of acrocentric chromosomes. A product containing thi s sequence was obtained by telomere-anchored PCR using as a primer an oligonucleotide sequence from the cloned fragment. Our data suggest de methylation of cytosines at the cloned Not I site and in neighboring D NA in some tumors, compared with normal tissue, and suggest a greater similarity between human and chimpanzee subtelomeric sequences than wa s previously reported.