LOOP-SIZE SPACINGS BETWEEN CGCG CLUSTERS IN LONG SEGMENTS OF HUMAN DNA

The CGCG tetranucleotides are clustered inside the CpG islands in the genomes of vertebrates. In order to study the distribution of the isla nds in the human chromosome we have mapped the loci sensitive to the C GCG specific restriction nuclease, in a 1.5 Mb long DNA segment cloned as Yeast Artificial Chromosome (YAC). The sites most sensitive to Bsh 1236 I nuclease show chromosomal loop-size spacing. This result, as w ell as the result of nucleotide sequence analysis of long genomic segm ents, suggests that the CGCG are organised in dusters (not always unde rmethylated) which are coincident with GC peaks on the sine wavelike c urve representing DNA composition along the mammalian chromosome. (C) 1995 Academic Press, Inc.