The Drosophila Na,K-ATPase alpha-subunit gene: gene structure, promoter function and analysis of a cold-sensitive recessive-lethal mutation.
The Drosophila Na,K-ATPase (or sodium pump) alpha-subunit gene was found to contain 10 exons and span approx. 25 kb. Two nearly adjacent transcriptional initiation sites were identified, and the 2085-nucleotide sequence upstream of the first transcriptional start was analysed for promoter activity in transfected Drosophila SL2 cells. This region was found to contain many cis-acting elements that influence promoter activity, including elements that confer 2- to 3-fold higher activity in SL2 cells cultured at 30 degrees C versus 22 degrees C. Temperature-sensitive transcriptional regulation of the Na,K-ATPase alpha-subunit in Drosophila is a plausible mechanistic candidate for the factor driving temperature-dependent up-regulation of the Na,K-ATPase alpha-subunit described here for fly strains homozygous for single P-element insertions in the alpha-subunit gene. Four new P-element insertion strains were identified in this study, each insertion site lying within the first intron of the Na,K-ATPase alpha-subunit gene. The insertion in strain 0462 resulted in cold-sensitive recessive lethality; flies homozygous for the 0462 mutation could be rescued by growth at 29-30 degrees C, a condition that partially corrected a deficiency in the level of Na,K-ATPase alpha-subunit. The high-temperature rescue of homozygous 0462 flies appeared to result primarily from improved Na,K-ATPase expression rather than an increase in the rate of ion transport per Na,K-ATPase molecule. These observations point to a role for sodium-pump activity in determining the range of temperature tolerance in Drosophila and demonstrate that relatively subtle changes in sodium-pump expression can have major consequences in whole organisms.
Feng
Y
Y
Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
Huynh
L
L
Takeyasu
K
K
Fambrough
D M
DM
D000222:Adaptation, Physiological; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA; D018983:DNA Footprinting; D004251:DNA Transposable Elements; D004330:Drosophila / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D005091:Exons; D005804:Genes, Lethal; D005808:Genes, Recessive; D006579:Heterozygote; D006720:Homozygote; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism; D013696:Temperature; D014158:Transcription, Genetic
D004251:DNA Transposable Elements; D004247:DNA; D000254:Sodium-Potassium-Exchanging ATPase