Johnson D H
Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, FL 33136-1019.
Mol Gen Genet. 1993 Apr;238(3):383-9. doi: 10.1007/BF00291997.
The Aprt locus of Drosophila encodes the structural gene for the purine salvage enzyme adenine phosphoribosyltransferase. Aprt is autosomal and enzyme activity is gene-dose-dependent in Drosophila melanogaster. However, Aprt is X-linked and dosage compensated in Drosophila pseudoobscura, as shown here. The Aprt genes of both Drosophila species contain a DNA sequence associated with nuclear matrix attachment sites and these Aprt sequences specifically bind to nuclear matrix in vitro. Putative promoter sequences positioned upstream of the predicted transcriptional start site in the two Aprt genes have a similar structure of direct repeats with an overlapping dyad symmetry, but the DNA sequence of these motifs is not conserved between the two species. Biological features in mutants of Aprt as well as natural variants suggest that dosage compensation of this gene in Drosophila pseudoobscura is due to a general control mechanism on X-linked genes rather than a gene-specific mechanism.
果蝇的Aprt基因座编码嘌呤补救酶腺嘌呤磷酸核糖转移酶的结构基因。Aprt是常染色体基因，在黑腹果蝇中酶活性呈基因剂量依赖性。然而，如下所示，Aprt在拟暗果蝇中是X连锁且剂量补偿的。两种果蝇的Aprt基因都包含与核基质附着位点相关的DNA序列，并且这些Aprt序列在体外能特异性结合核基质。在两个Aprt基因中，位于预测转录起始位点上游的推定启动子序列具有直接重复的相似结构，带有重叠的二元对称，但这两个物种之间这些基序的DNA序列并不保守。Aprt突变体以及自然变体的生物学特征表明，拟暗果蝇中该基因的剂量补偿是由于对X连锁基因的一般控制机制，而非基因特异性机制。
