Cooperative sequence modules determine replication initiation sites at the human beta-globin locus.
The human beta globin locus contains two adjacent replicators, each capable of initiating DNA replication when transferred from its native locus to ectopic sites. Here, we report a detailed analysis of the sequence requirements for replication initiation from these replicators. In both replicators, initiation required a combination of an asymmetric purine:pyrimidine sequence and several AT-rich stretches. Modules from the two replicators could combine to initiate replication. AT-rich sequences were essential for replicator activity: a low frequency of initiation was observed in DNA fragments that included a short stretch of AT-rich sequences, whereas inclusion of additional AT-rich stretches increased initiation efficiency. By contrast, replication initiated at a low level without the asymmetric purine:pyrimidine modules but they were required in synergy to achieve efficient initiation. These data support a combinatorial model for replicator activity and suggest that the initiation of DNA replication requires interaction between at least two distinct sequence modules.
Wang
Lixin
L
Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, MD 20892, USA.
Lin
Chii Mei
CM
Lopreiato
Joseph O
JO
Aladjem
Mirit I
MI
D001483:Base Sequence; D002460:Cell Line; D017124:Conserved Sequence; D018899:CpG Islands; D004261:DNA Replication; D005914:Globins / Q000235:genetics*; D006801:Humans; D019901:Locus Control Region; D008969:Molecular Sequence Data; D018741:Replication Origin; D014158:Transcription, Genetic
D005914:Globins