Isolation and characterization of a family of sequences dispersed on the human X chromosome.
During a systematic search for X-specific sequences we isolated a DNA fragment (called G1.3) that hybridizes to six further homologous X-specific genomic fragments that map to at least four different regions of the human X chromosome. Genomic segments of 11-30 kb (called G1.3 a, b, c, d, and e or DNF22S1 to DNF22S5) have been subsequently cloned for five of the seven repetitions and characterized by restriction mapping. Single-copy sequences have been used to analyze homology between cloned repetitions, to confirm X specificity, and to regionally localize the repetitions. Sequence homology between members of this family seems to be very high (80-90%) and to extend over at least 5 to 12 kb. In situ hybridization and Southern blotting experiments with a panel of human-rodent hybrid cell lines demonstrated that four of the cloned sequences map to three different regions within Xp21.2-pter and the fifth one (G1.3c) maps to Xq28. The family is present with the same complexity and X specificity in macaques (20-30 x 10(6) years divergence with man), whereas no related sequences were detected in the mouse. To our knowledge small families of dispersed chromosome-specific sequences have been described only for the human Y chromosome. The possible functional or evolutionary significance of this family is discussed.
Bardoni
B
B
Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
Guioli
S
S
Raimondi
E
E
Heilig
R
R
Mandel
J L
JL
Ottolenghi
S
S
Camerino
G
G
D000818:Animals; D002460:Cell Line; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D008040:Genetic Linkage; D006801:Humans; D006822:Hybrid Cells / Q000166:cytology; D009693:Nucleic Acid Hybridization; D009710:Nucleotide Mapping; D014960:X Chromosome
D004262:DNA Restriction Enzymes