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PubMed1999

Drosophila Src42A is a negative regulator of RTK signaling.

The Src family of nonreceptor tyrosine kinases has been implicated in many signal transduction pathways. However, due to a possible functional redundancy in vertebrates, there is no genetic loss-of-function evidence that any individual Src family member has a crucial role for receptor tyrosine kinase (RTK) signaling. Here we show that an extragenic suppressor of Raf, Su(Raf)1, encodes a Drosophila Src family gene Src42A. Characterization of Src42A mutations shows that Src42A acts independent of Ras1 and that it is, unexpectedly, a negative regulator of RTK signaling. Our study provides the first evidence that Src42A defines a negative regulatory pathway parallel to Ras1 in the RTK signaling cascade. A possible model for Src42A function is discussed.

Alleles↗
PubMed1999

bloated tubules (blot) encodes a Drosophila member of the neurotransmitter transporter family required for organisation of the apical cytocortex.

We have identified a novel member of the vertebrate sodium- and chloride-dependent neurotransmitter symporter family from Drosophila melanogaster. This gene, named bloated tubules (blot), shows significant sequence similarity to a subgroup of vertebrate orphan transporters. blot transcripts are maternally supplied and during embryogenesis exhibit a complex and dynamic pattern in a subset of ectodermally derived epithelia, notably in the Malpighian tubules, and in the nervous system. Animals mutant for this gene are larval lethals, in which the Malpighian tubule cells are distended with an enlarged and disorganised apical surface. Embryos lacking the maternal component of blot expression die during early stages of development. They show an inability to form actin filaments in the apical cortex, resulting in impaired syncytial nuclear divisions, severe defects in the organisation of the cortical cytoskeleton, and a failure to cellularise. For the first time, a neurotransmitter transporter-like protein has been implicated in a function outside the nervous system. The isolation of blot thus provides the basis for an analysis of the relationship between the function of this putative transporter and epithelial morphogenesis.

Amino Acid Sequence↗
PubMed1993

Relationship between scaffold-attached regions, sequences replicating autonomously in yeast, and a chromosomal replication origin in the Drosophila rDNA.

The potential relationship between anchorage of Drosophila rDNA to a nuclear substructure and replication mechanisms was studied. First, two scaffold-attached regions (SARs) were identified, in the internally transcribed spacer and in the region spanning both the intergenic spacer (IGS) and the externally transcribed spacer (ETS), respectively. These SARs define two possible loops containing the sequence coding for the 18S rRNA and part of that coding for the 28S rRNA, respectively. They also bind yeast scaffolds. Then, the presence of sequences able to promote extrachromosomal replication in yeast (ARSs) was tested. The identified ARSs comap with SARs. The tight relationship between SARs and ARSs was further investigated in the IGS-ETS region which contains a chromosomal replication origin. The topological correlation observed between SARs, ARSs, and a chromosomal replication origin suggests the physical association of the replication origin to the nuclear substructure.

Animals↗
PubMed1995

Trypanozoon: infectivity to humans is linked to reduced transmissibility in tsetse. II. Genetic mechanisms.

Trypanozoon infections are less likely to mature in female tsetse than in males. Analysis of maturation data from 37 Trypanozoon isolates in Glossina m. morsitans showed that while the proportion of mature infections (salivary gland infections as a proportion of established midgut infections) varied from isolate to isolate, the proportion of mature infections in female flies was consistently smaller than the proportion in male flies. The log of the probability of maturation in females is, on average, twice the log of the probability in males (estimate of the ratio of the logged proportions is 2.09, 95% confidence interval (CI) 1.8 to 2.5). Human serum-resistant isolates were less likely to mature than human serum-sensitive isolates (ratio of logged proportions maturing was 1.5, 95% CI 1.3 to 1.8, in both male and female tsetse). Data for four other trypanosome stocks show that the probability of maturation decreases as the maturation time (the delay between the infected bloodmeal and maturation) increases. The decrease is approximately exponential with twice the half-life in male flies compared to that in female flies (estimate of the ratio of the exponential parameters is 1.97, 95% CI 0.7 to 3.3). A model is proposed to explain these observations which assumes that product(s) from an X-linked gene(s) kills or otherwise prevents migrating parasites from establishing a mature infection. Longer maturation times are associated with a heavy penalty in terms of transmissibility as measured by the vectorial capacity.

Animals↗
PubMed1994

Genomic cloning and chromosomal localization of HRY, the human homolog to the Drosophila segmentation gene, hairy.

The Drosophila hairy gene encodes a basic helix-loop-helix protein that functions in at least two steps during Drosophila development: (1) during embryogenesis, when it partakes in the establishment of segments, and (2) during the larval stage, when it functions negatively in determining the pattern of sensory bristles on the adult fly. In the rat, a structurally homologous gene (RHL) behaves as an immediate-early gene in its response to growth factors and can, like that in Drosophila, suppress neuronal differentiation events. Here, we report the genomic cloning of the human hairy gene homolog (HRY). The coding region of the gene is contained within four exons. The predicted amino acid sequence reveals only four amino acid differences between the human and rat genes. Analysis of the DNA sequence 5' to the coding region reveals a putative untranslated exon. To increase the value of the HRY gene as a genetic marker and to assess its potential involvement in genetic disorders, we sublocalized the locus to chromosome 3q28-q29 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1995

Structural organization and genetic localization of the human bone morphogenetic protein 1/mammalian tolloid gene.

Bone morphogenetic protein 1 (BMP1) is a putative protease purified from extracts capable of inducing ectopic bone formation. A single mammalian gene apparently encodes alternatively spliced transcripts for BMP1, for a longer protein with a domain structure identical to that of the Drosophila dorsal-ventral patterning gene product tolloid (Tld), and for a third species of low abundance. Here we describe the organization of the 46-kb, 22-exon human BMP1/mTld gene that encodes these forms. Exons corresponding to each of the alternatively spliced transcripts are identified, and comparison with the Drosophila Tld gene reveals alignment of introns at only three positions. The major BMP1/mTld transcription start site is found only 706 bp downstream of the polyadenylation site of the SFTP2 surfactant gene, and a previously reported highly polymorphic CA repeat is found within the BMP1/mTld first intron. These two findings place the BMP1/mTld gene between markers D8S298 and D8S5 on the genetic map.

Alternative Splicing↗
PubMed1999

Invertebrate tissue inhibitor of metalloproteinase: structure and nested gene organization within the synapsin locus is conserved from Drosophila to human.

Vertebrate tissue inhibitors of metalloproteinases (TIMPs) regulate extracellular matrix metalloproteinases and are thus involved in a wide variety of developmental and physiological processes. By identifying cDNAs of a transcript detected within an intron of the Drosophila synapsin gene we have cloned the Drosophila TIMP gene (Timp), which represents the first invertebrate member of the TIMP gene family. Sequence analysis revealed an open reading frame of 210 amino acids with 35% identity to human TIMPs and a conserved exon-intron structure. Analysis of sequence data from the Sanger Centre demonstrated that the human TIMP3 gene is encoded within intron V of the human synapsin-III gene, indicating that the nested organization of TIMP and synapsin genes may be a general feature conserved in evolution. We therefore speculate that the human TIMP4 gene will be located in intron V of the human synapsin-II gene on chromosome 3p25, and we present preliminary evidence that a human synapsin-IV gene is located near the TIMP2 gene on chromosome 17q23-q25.

Amino Acid Sequence↗
PubMed2000

Cloning, expression, and chromosomal localization of a mouse gene homologous to the germ cell migration regulator wunen and to type 2 phosphatidic acid phosphatases.

The wunen gene of Drosophila melanogaster encodes a multipass membrane-spanning protein that negatively regulates primordial germ cell migration. Here we describe the cloning of a mouse gene that encodes a protein homologous to wunen and to the Type 2 phosphatidic acid phosphatases. This gene encodes a 251-amino-acid protein that most closely resembles the human Type 2 phosphatidic acid phosphatase PAP-2c. Northern blot analysis revealed the presence of a single 1.9-kb Ppap2c transcript. The Ppap2c gene was localized to the central portion of mouse Chromosome 10 by interspecific backcross analysis.

Amino Acid Sequence↗
PubMed1996

Molecular characterization of the 71E late puff in Drosophila melanogaster reveals a family of novel genes.

Early metamorphic development in Drosophila melanogaster is initiated by pulses of the steroid hormone ecdysone, which are transduced into tissue-specific transcriptional cascades. This process begins with the hormone-dependent activation of a set of transcription factors (early genes) that, in turn, activate set of tissue-specific effector genes (late genes). The 71E cytogenetic region of the salivary gland polytene genome contains several ecdysone-regulated transcription units. Molecular techniques were used to analyze these genes, their transcriptional program and their evolutionary relatedness. We find that this region contains a cluster of ten coordinately regulated late genes (L71 genes) that are organized as five divergently transcribed gene pairs. Maximum parsimony analysis suggests that an ancestral L71 gene duplicated to form the first gene pair which was, in turn, duplicated to form the set of gene pairs. The L71 gene products form a family of small, chemically basic proteins with a conserved backbone of cysteine residues. In addition, the 71E region contains another gene (I71-1) with the regulatory and biochemical characteristics of the salivary gland intermolt glue proteins.

Amino Acid Sequence↗
PubMed1996

Quetzal: a transposon of the Tc1 family in the mosquito Anopheles albimanus.

A member of the Tc1 family of transposable elements has been identified in the Central and South American mosquito Anopheles albimanus. The full-length Quetzal element is 1680 base pairs (bp) in length, possesses 236 bp inverted terminal repeats (ITRs), and has a single open reading frame (ORF) with the potential of encoding a 341-amino-acid (aa) protein that is similar to the transposases of other members of the Tc1 family, particularly elements described from three different Drosophila species. The approximately 10-12 copies per genome of Quetzal are found in the euchromatin of all three chromosomes of A. albimanus. One full-length clone, Que27, appears capable of encoding a complete transposase and may represent a functional copy of this element.

Amino Acid Sequence↗
PubMed1993

Homopolymer length variation in the Drosophila gene mastermind.

Runs of identical amino acids encoded by triplet repeats (homopolymers) are components of numerous proteins, yet their role is poorly understood. Large numbers of homopolymers are present in the Drosophila melanogaster mastermind (mam) protein surrounding several unique charged amino acid clusters. Comparison of mam sequences from D. virilis and D. melanogaster reveals a high level of amino acid conservation in the charged clusters. In contrast, significant divergence is found in repetitive regions resulting from numerous amino acid replacements and large insertions and deletions. It appears that repetitive regions are under less selective pressure than unique regions, consistent with the idea that homopolymers act as flexible spacers separating functional domains in proteins. Notwithstanding extensive length variation in intervening homopolymers, there is extreme conservation of the amino acid spacing of specific charge clusters. The results support a model where homopolymer length variability is constrained by natural selection.

Amino Acid Sequence↗
PubMed1994

A cluster of esterase genes on chromosome 3R of Drosophila melanogaster includes homologues of esterase genes conferring insecticide resistance in Lucilia cuprina.

We identify an esterase isozyme in Drosophila melanogaster, EST 23, which shares biochemical, physiological, and genetic properties with esterase E3, which is involved in resistance to organophosphate insecticides in Lucilia cuprina. Like E3, the D. melanogaster EST 23 is a membrane-bound alpha-esterase which migrates slowly toward the anode at pH 6.8. Both enzymes have similar preferences for substrates with shorter acid side chain lengths. Furthermore, on the basis of their high sensitivity to inhibition by paraoxon and their insensitivity to inhibition by eserine sulfate, both enzymes were classified as subclass I carboxylesterases. The activity of each enzyme peaks early in development and, again, in the adult stage. Both enzymes are found in the male reproductive system and larval and adult digestive tissues, the latter being consistent with a role for these enzymes in organophosphate resistance. Fine structure deficiency mapping localized Est 23 to cytological region 84D3 to E1-2 on the right arm of chromosome 3. Moreover, we show that the genes encoding three other esterase phenotypes also map to the same region; these phenotypes involve allozymic differences in EST 9 (formerly EST C), ali-esterase activity, defined by the hydrolysis of methyl butyrate, and malathion carboxylesterase activity, defined by hydrolysis of the organophosphate malathion. This cluster corresponds closely to that encompassing E3 and malathion carboxylesterase on chromosome 4 in L. cuprina, the homologue of chromosome 3R in D. melanogaster.

Animals↗
PubMed1992

The suppressor of Hairy-wing binding region is required for gypsy mutagenesis.

We undertook a deletional analysis of the gypsy retrotransposon in order to determine which sequences of the element are required for its mutagenic effect. We show that a phenotype indistinguishable from that of y2 flies can be generated by transforming y- flies with a construct containing the yellow gene and a gypsy element located at the same insertion site in yellow as found in y2 flies. When flies are transformed with similar constructs in which increasing amounts of the 5' transcribed untranslated region of gypsy have been removed, either a partial y2 revertant or a completely revertant phenotype is obtained. These results yield direct proof that the region of gypsy to which the su(Hw) protein binds is required for the generation of mutant phenotypes by this retrotransposon.

Amino Acid Sequence↗
PubMed1995

Mapping functional domains of the polycomb protein of Drosophila melanogaster.

In Drosophila the Polycomb group (Pc-G) proteins are responsible for the stable and heritable silencing of genes. The Pc-G apparently uses heterochromatin-like mechanisms to transcriptionally inactivate developmental regulators such as the homeotic genes. The Polycomb (Pc) protein is part of a large multimeric complex composed of other members of the Pc-G. We have identified functionally relevant domains of the Pc protein by sequencing different Pc alleles. Additionally, using a Pc-beta gal fusion protein with deleted internal histidine repeats, we found that this mutant protein cannot bind to four particular target loci, but otherwise does not change the remaining overall binding pattern. We show that, in contrast to the dotted subnuclear localization of the wild-type protein, the nuclear distribution of mutant proteins becomes homogeneous. Surprisingly, in Pc mutants the polyhomeotic protein, another member of the Pc-G, is also redistributed in the nucleus. Our results indicate that the appropriate subnuclear localization of the two proteins is critical for the silencing function of the Pc-G complex.

Alleles↗
PubMed1996

A newly identified Minute locus, M(2)32D, encodes the ribosomal protein L9 in Drosophila melanogaster.

A gene encoding a ubiquitously expressed mRNA in Drosophila melanogaster was isolated and identified as the gene for ribosomal protein L9 (rpL9) by its extensive sequence homology to the corresponding gene from rat. The rpL9 gene is localized in polytene region 32D where two independent P element insertions flanking the locus are available. Remobilization of either P element generated lines with a typical Minute phenotype, e.g. thin and short bristles, prolonged development, and female semisterility in heterozygotes as well as homozygous lethality. All these characteristics can be rescued when a 3.9 kb restriction fragment containing the rpL9 gene is reintroduced by P element-mediated germline transformation. This result confirms that M(2)32D codes for ribosomal protein L9.

Amino Acid Sequence↗
PubMed2003

Frequent mitochondrial gene rearrangements at the hymenopteran nad3-nad5 junction.

We characterized the organization of mitochondrial genes from a diverse range of hymenopterans. Of the 21 taxa characterized, 12 had distinct, derived organizations. Some rearrangements were consistent with the duplication-random loss mechanism, while others were not. Local inversions were relatively common, i.e., rearrangements characterized by the movement of genes from one mitochondrial strand to the other, opposite or close to their ancestral position. This type of rearrangement is inconsistent with the duplication/random loss model of mitochondrial gene rearrangement. Instead, they are best explained by the operation of recombination. Taxa with derived organizations were restricted to a single, monophyletic group of wasps, the Apocrita, which comprise about 90% of all hymenopterans.

Animals↗
PubMed2006

Abundance and chromosomal distribution of six Drosophila buzzatii transposons: BuT1, BuT2, BuT3, BuT4, BuT5, and BuT6.

The abundance and chromosomal distribution of six class-II transposable elements (TEs) of Drosophila buzzatii have been analyzed by Southern blotting and in situ hybridization. These six transposons had been previously found at the breakpoints of inversions 2j and 2q ( 7 ) of D. buzzatii. These two polymorphic inversions were generated by an ectopic recombination event between two copies of Galileo, a Foldback element. The four breakpoints became hotspots for TE insertions after the generation of the inversion and the transposons analyzed in this work are considered to be secondary invaders of these regions. Insertions of the six transposons are present in the euchromatin but show an increased density in the pericentromeric euchromatin-heterochromatin transition region and the dot chromosome. They are also more abundant in the inverted segments of chromosome 2 rearrangements. We further observed that the accumulation of TE insertions varies between elements and is correlated between dot, proximal regions, and inverted segments. These observations fully agree with previous data in Drosophila melanogaster and support recombination rate as the chief force explaining the chromosomal distribution of TEs.

Animals↗