Monoclonal antibodies have been used to identify three proteins in Drosophila melanogaster that share antigenic determinants with the major heat shock proteins hsp7O and hsp68. While two of the proteins are major proteins at all developmental stages, one heat shock cognate protein, hsc7O, is especially enriched in embryos. hsc7O is shown to be the product of a previously identified gene, Hsc4. We have examined the levels of hsp7O-related proteins in adult flies and larvae during heat shock and recovery. At maximal induction in vivo, hsp7O and hsp68 never reach the basal levels of the major heat shock cognate proteins. Monoclonal antibodies to hsc7O have been used to localize it to a meshwork of cytoplasmic fibers that are heavily concentrated around the nucleus.Drosophila melanogaster responds to growth at elevated temperature and a number of other stresses by suppressing normal protein synthesis and inducing or enhancing the synthesis of seven heat shock proteins (hsps), hsp70, -68, -83, -27, -26, -23, and -22 (4). The characteristic vigorous induction of a small number of evolutionarily conserved heat shock genes is now known to be a universal cellular response to stress. This response has been observed in a broad spectrum of eucaryotes, including plants, and also in the procaryote Escherichia coli (61). The mechanism of induction common to these inducers and the functions of the hsps are unknown. There is good evidence that the stress response is an adaptive mechanism that enables cells to survive a variety of environmental conditions that would otherwise be lethal (2,17,34,36,38).It is clear that the D. melanogaster heat shock genes are not coordinately expressed during normal development. hsp83 is probably present in all normal cells, and its induction after heat shock results in only a few fold increase in protein (33,40,76). mRNAs for hsp27 and -26 are synthesized during oogenesis and can be detected until the blastoderm stage (76). All four small hsps are induced in response to ecdysone during puparium formation (8, 25, 26, 58).In D. melanogaster, the Hsp7O gene family consists of both heat-inducible and constitutively expressed genes. hsp70 and hsp68 (which share 75% homology) are virtually absent under nonstress conditions (68). There are two copies of Hsp7O at 87A, three to four copies at 87C, and one copy of Hsp68 at 95D. Craig and colleagues (9, 23) have discovered a family of genes, 75 to 80% homologous to Hsp7O, termed heat shock cognate genes, which are expressed under normal growth conditions. The three heat shock cognate genes identified, Hscl, -2, and -4, map cytologically to 70C, 87D, and 88E, respectively. The levels of RNA organisms (20,28,35,71,72,74). A family of genes encoding proteins homologous to the Hsp7O constitutive and inducible members has also been identified and isolated in yeasts (24). In E. coli, heat treatment stimulates the rates of synthesis of at least 17 proteins (39), of which DnaK and C62.5 have been shown to be homologous to hsp70 and hsp83, respectively, in D. me...

Regulatory Factor X (RFX) transcription factors (TFs) are best known for activating genes required for ciliogenesis in both vertebrates and invertebrates. In humans, eight RFX TFs have a variety of tissue-specific functions, while in the worm Caenorhabditis elegans, the sole RFX gene, daf-19, encodes a set of nested isoforms. Null alleles of daf-19 confer pleiotropic effects including altered development with a dauer constitutive phenotype, complete absence of cilia and ciliary proteins, and defects in synaptic protein maintenance. We sought to identify RFX/daf-19 target genes associated with neuronal functions other than ciliogenesis using comparative transcriptome analyses at different life stages of the worm. Subsequent characterization of gene expression patterns revealed one set of genes activated in the presence of DAF-19 in ciliated sensory neurons, whose activation requires the daf-19c isoform, also required for ciliogenesis. A second set of genes is downregulated in the presence of DAF-19, primarily in nonsensory neurons. The human orthologs of some of these neuronal genes are associated with human diseases. We report the novel finding that daf-19a is directly or indirectly responsible for downregulation of these neuronal genes in C. elegans by characterizing a new mutation affecting the daf-19a isoform (tm5562) and not associated with ciliogenesis, but which confers synaptic and behavioral defects. Thus, we have identified a new regulatory role for RFX TFs in the nervous system. The new daf-19 candidate target genes we have identified by transcriptomics will serve to uncover the molecular underpinnings of the pleiotropic effects that daf-19 exerts on nervous system function.

The Drosophila heat shock cognate gene 4 (hsc4), a member of the hsp70 gene family, encodes an abundant protein, hsc70, that is more similar to the constitutively expressed human protein than the Drosophila heat-inducible hsp70. Developmental expression revealed that hsc4 transcripts are enriched in cells active in endocytosis and those undergoing rapid growth and changes in shape.

Monoclonal antibodies have been used to identify three proteins in Drosophila melanogaster that share antigenic determinants with the major heat shock proteins hsp70 and hsp68. While two of the proteins are major proteins at all developmental stages, one heat shock cognate protein, hsc70, is especially enriched in embryos. hsc70 is shown to be the product of a previously identified gene, Hsc4. We have examined the levels of hsp70-related proteins in adult flies and larvae during heat shock and recovery. At maximal induction in vivo, hsp70 and hsp68 never reach the basal levels of the major heat shock cognate proteins. Monoclonal antibodies to hsc70 have been used to localize it to a meshwork of cytoplasmic fibers that are heavily concentrated around the nucleus.