title: Molecular organization and chromosomal location of human GC-rich heterochromatic blocks.
abstract: From the sequencing of three genomic DNA fragments and PCR amplification products from total human DNA, we have derived the sequence of a 545-bp Sau3A fragment (68% GC), representative of a family of human DNA repeats. Since previous studies suggested its linkage with unrelated Sau3A repeats of 68 bp (54% GC) (beta-satellite sequences), this feature was further investigated by in situ hybridization experiments and by Southern blot analysis of a panel of DNAs from human-Chinese hamster somatic cell hybrids. Both DNA repeats are preferentially localized on the heterochromatic regions of acrocentric chromosomes, on the pericentromeric heterochromatin of chromosome 1, 3 and 9, and on the proximal euchromatic region of the chromosome Y q arm. On chromosome 9, both repeats are part of a 2.7-kb higher-order repeat unit. These results and the Southern blot analysis on partial digests of total DNA, suggest that the linkage between the two repetitive DNA sequences is a constant feature throughout the genome. Furthermore, Southern blot analysis of HpaII-digested and MspI-digested DNA from different human tissues and tumor cell lines indicates that the investigated heterochromatic blocks appear to be subjected to changes in their methylation pattern.
authors.affiliation: Dipartimento di Biologia e Genetica per le Scienze Mediche, Università di Milano, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Meneveri
authors.forename: A
authors.initials: A
authors.lastname: Agresti
authors.forename: A
authors.initials: A
authors.lastname: Marozzi
authors.forename: S
authors.initials: S
authors.lastname: Saccone
authors.forename: M
authors.initials: M
authors.lastname: Rocchi
authors.forename: N
authors.initials: N
authors.lastname: Archidiacono
authors.forename: G
authors.initials: G
authors.lastname: Corneo
authors.forename: G
authors.initials: G
authors.lastname: Della Valle
authors.forename: E
authors.initials: E
authors.lastname: Ginelli
mesh_terms: D001483:Base Sequence / Q000235:genetics; D002874:Chromosome Mapping; D003562:Cytidine; D015252:Deoxyribonucleases, Type II Site-Specific; D006147:Guanine; D006570:Heterochromatin / Q000737:chemistry*; D006801:Humans; D008745:Methylation; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*
chemical_list: D006570:Heterochromatin; D003562:Cytidine; D006147:Guanine; D015252:Deoxyribonucleases, Type II Site-Specific; C024405:GATC-specific type II deoxyribonucleases