We determined the nucleotide sequence of genomic DNA corresponding to the yellow gene. The limits of the transcribed region were deduced from sequence analysis of yellow larval and pupal cDNA clones. The yellow transcription unit is simple, composed of two exons which are processed identically in both developmental stages into a mRNA of 1990 bp. The predicted yellow protein has a mol. wt of 60,752 daltons and appears to be a secreted protein having a structural function and not an enzymatic role in pigmentation. We also characterized the spontaneous mutation y2 and a revertant of this allele to investigate the mutagenic effect of the gypsy element inserted into this locus. Our results show that this transposon is inserted at ‐700 bp and that the y2+ revertant resulted from excision of the gypsy element leaving behind a complete long terminal repeat (LTR). We conclude, therefore, that the gypsy element is neither inserted into a pupal specific intron or regulatory sequence supporting the hypothesis that mutagenesis is a result of transcriptional interference by the gypsy element on the yellow gene.
The Src family of tyrosine protein kinases represent an expanding class of closely related intracellular enzymes that participate in the signal transduction pathways of a variety of surface receptors. One of the more surprising aspects of the information relating Src protein kinases to receptor signaling is the apparent diversity of receptor types with which the Src-related enzymes are reported to interact physically or functionally. Traditional biochemical and genetic approaches have yielded much information regarding the interactions between the Src tyrosine protein kinases and other cellular proteins in defined cell types, and emerging technologies, most notably homologous recombination in embryonal stem cells to achieve gene "knockouts," are providing new insights into the participation of the Src-related gene products in signal transduction and development.
Some transposable elements affect the genes they mutate by bringing their expression under the control of a second unlinked locus that is termed a modifier. The modifier gene is referred to as an enhancer or a suppressor locus, depending on the type of effect exerted by mutations in this gene on the phenotype of the transposable element-induced mutation. This type of phenomenon has been documented extensively in yeast and Drosophila (for reviews, see Roeder and Fink 1983;Rubin 1983;Kubli 1986; Parkhurst and Corces 1986b;Rutledge et al. 1988
The suppressor of Hairy-wing [su(Hw)] locus encodes a zinc finger-containing protein that binds to specific sequences of the Drosophila gypsy element, mediating the mutagenic effects of this retrotransposon. We carried out a detailed analysis of the su(Hw)-gypsy interaction using various biochemical assays. DNase I footprinting delimits a 37-bp region in the coding strand of gypsy that is protected from digestion by the binding of the su(Hw) protein. Specific DNA contacts involved in the interaction were determined by methylation protection analysis and by missing nucleoside experiments using hydroxyl radical. Results from these experiments indicate that the su(Hw) protein binds to sequences homologous to the octamer motif, which is recognized by homeo box-containing proteins in mammalian organisms. Furthermore, two DNA bends present on both sides of the binding site in the absence of protein favor the strength of this interaction.
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