Molecular characterization of Drosophila genes encoding a G protein alpha subunit and a phospholipase C that are expressed in the central nervous system
Abstract
Two Drosophila genes (dgo and p21) have been isolated and characterized. The dgo gene encoding a G protein $\alpha$ subunit has been isolated by screening genomic and adult head cDNA libraries using bovine transducin $\alpha$ subunit cDNA as probe, and the p21 gene encoding a PLC has been isolated by screening a genomic library using Drosophila norpA (a PLC gene involved in phototransduction) cDNA as probe. The dgo gene, which maps to 47A on the second chromosome, encodes two proteins which are both 354 amino acids long but differ in seven amino acids in the amino terminal region. The deduced amino-acid sequences of the two proteins are 81% identical to that of a rat G$\sb{\rm o} \alpha$ subunit. Analysis of genomic clones revealed that there are eight coding exons and that the putative transcripts for the two proteins differ in the 5$\sp\prime$-noncoding regions and the first coding exons but share the remaining six coding exons. The arrangement of two different 5$\sp\prime$-noncoding regions on the gene suggests that two different promoters regulate the expression of the transcripts encoding the two proteins. RNA blot analysis detected three transcripts: a 3.9 kb transcript found at all stages of development, a 5.4 kb transcript present predominantly in adult heads, and a 3.4 kb transcript present only in adult bodies. In situ hybridizations of a cDNA probe to adult tissue sections showed that the gene is expressed abundantly in neuronal cell bodies in the brain, optic lobe, and thoracic ganglia. The p21 gene, which maps to 21C on the second chromosome, encodes two proteins which are 1305 and 1312 amino acids long. The two deduced protein sequences are similar in sequence and overall structure to the $\beta$-class of mammalian PLCs and differ only by seven consecutive amino acids present near C-terminus of one of the proteins, but not the other. Partial analysis of genomic clones provided the evidence for alternative splicing responsible for this difference between two deduced protein sequences. RNA blot analysis detected two prominent transcripts: a 5.6 kb transcript expressed throughout development, and a 7.0 kb transcript found only in adult heads. In situ hybridization of a cDNA probe to adult tissue sections showed that the gene is expressed abundantly in neuronal cell bodies in the brain, optic lobe, and thoracic ganglia. The developmental profiles of the dgo and p21 transcripts were very similar to each other. Furthermore, in situ hybridizations of dgo and p21 cDNAs to adjacent sections of adult and larvae showed nearly identical distributions of the transcripts in the nervous system. The results suggest that dgo and p21 genes are involved in the same signal transduction pathways of Drosophila.
Degree
Ph.D.
Advisors
Pak, Purdue University.
Subject Area
Molecular biology|Neurology
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