Molecular organization and chromosomal location of human GC-rich heterochromatic blocks.
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.
Meneveri
R
R
Dipartimento di Biologia e Genetica per le Scienze Mediche, Università di Milano, Italy.
Agresti
A
A
Marozzi
A
A
Saccone
S
S
Rocchi
M
M
Archidiacono
N
N
Corneo
G
G
Della Valle
G
G
Ginelli
E
E
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*
D006570:Heterochromatin; D003562:Cytidine; D006147:Guanine; D015252:Deoxyribonucleases, Type II Site-Specific; C024405:GATC-specific type II deoxyribonucleases