CONCERTED EVOLUTION OF PRIMATE ALPHA-SATELLITE DNA - EVIDENCE FOR AN ANCESTRAL SEQUENCE SHARED BY GORILLA AND HUMAN X-CHROMOSOME ALPHA-SATELLITE

[摘要] To understand evolutionary events in the formation of higher-order repeat units in alpha satellite DNA, we have examined gorilla sequences homologous to human X chromosome alpha satellite. In humans, alpha satellite on the X chromosome is organized as a tandemly repeated, 2.0 .times. 103 base-pairs (bp) higher-order repeat unit, operationally defined by the restriction enzyme BamHI. Each higher-order repeat unit is composed of 12 tandem approximately 171 base-pair monomer units that have been classified into five distinct sequence homology groups. BamHI-digested gorilla genomic DNA hybridized with the cloned human 2 .times. 103 bp X alpha satellite repeat reveals three bands of sizes approximately 3.2 .times. 103, 2.7 .times. 103 and 2 .times. 103 bp. Multiple copies of all three repeat lengths have been isolated and mapped to the centromeric region of the gorilla X chromosome by fluorescence in situ hybridization. Long-range restriction mapping using pulsed-field gel electrophoresis shows that the 2.7 .times. 103 and 3.2 .times. 103 bp repeat arrays exist as separate but likely neighboring arrays on the gorilla X, each ranging in size from approximately 200 .times. 103 to 500 .times. 103 bp, considerably smaller than the approximately 2000 .times. 103 to 4000 .times. 103 bp array found on human X chromosomes. Nucleotide sequencies analysis has revealed that monomers within all three gorilla repeat units can be classified into the same five sequence homology groups as monomers located within the higher-order repeat unit on the human X chromosome, suggesting that the formation of the five distinct monomer types predates the divergence of the lineages of contemporary humans and gorillas. The order of 12 monomers within the 2 .times. 103 and 2.7 .times. 103 bp repeat units from the gorilla X chromosomes is identical with that of the 2 .times. 103 bp repeat unit from the human X chromosome, suggesting an ancestral linear arrangement and supporting hypotheses about events largely restricted to single chromosome types in the formation of alpha satellite higher-order repeat units.

[发布日期] 1990-12-05