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J Clin Invest. 1988 May;81(5):1323-7.

Adenosine deaminase (ADA) deficiency due to deletion of the ADA gene promoter and first exon by homologous recombination between two Alu elements.

Author information

1
Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710.

Abstract

In 15-20% of children with severe combined immunodeficiency (SCID), the underlying defect is adenosine deaminase (ADA) deficiency. The goal of this study was to determine the precise molecular defect in a patient with ADA-deficient SCID whom we previously have shown to have a total absence of ADA mRNA and a structural alteration of the ADA gene. By detailed Southern analysis, we now have determined that the structural alteration is a deletion of approximately 3.3 kb, which included exon 1 and the promoter region of the ADA gene. DNA sequence analysis demonstrates that the deletion created a novel, complete Alu repeat by homologous recombination between two existing Alu repeats that flanked the deletion. The 26-bp recombination joint in the Alu sequence includes the 10-bp "B" sequence homologous to the RNA polymerase III promoter. This is the first example of homologous recombination involving the B sequence in Alu repeats. Similar recombination events have been identified involving Alu repeats in which the recombination joint was located between the A and B sequences of the polymerase III split promoter. The nonrandom location of these events suggests that these segments may be hot spots for recombination.

PMID:
3366897
PMCID:
PMC442559
DOI:
10.1172/JCI113458
[Indexed for MEDLINE]
Free PMC Article

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