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We have analysed CpG frequency and CpG methylation across part of the human alpha-globin locus. Clusters of CpG at the alpha 1 and alpha 2 genes resemble the 'HpaII tiny fragment (HTF) islands' that are characteristic of mammalian 'housekeeping' genes: CpG frequency is not suppressed; testable CpGs are not methylated in DNA from erythroid or nonerythroid tissues, although flanking CpGs are methylated; CpG clusters are approximately 1.5 kb long and extend both upstream and downstream of the alpha-globin transcription start site. These features are not found at genes of the beta-globin locus. The alpha-globin pseudogene (psi alpha 1) is highly homologous to the alpha 2 and alpha 1 genes, but it lacks an HTF island. Sequence comparison shows that a high proportion of CpGs in the alpha 2 gene are substituted by TpG or CpA in the pseudogene. This strongly suggests that an ancestral HTF island at the pseudogene became methylated in the germline, and was lost due to the mutability of 5-methylcytosine.

Type

Journal article

Journal

Embo J

Publication Date

1987

Volume

6

Pages

999 - 1004

Keywords

Base Sequence Bone Marrow/metabolism Cytidine Monophosphate/analogs & derivatives/*analysis Cytosine Nucleotides/*analysis DNA/isolation & purification *Evolution *Genes, Structural Globins/*genetics Guanosine/*analogs & derivatives/analysis Human Male Methylation Spermatozoa/metabolism Support, Non-U.S. Gov't Tissue Distribution Transcription, Genetic