Drosophila melanogaster U1 snRNA genes

We have isolated and characterized a recombinant which contains a Drosophila melanogaster U1 small nuclear RNA (snRNA) gene colinear with the published snRNA sequence. Southern hybridizations of the fly genomic DNA, using as probe a plasmid containing only the coding region of the gene, shows that the fly contains at most three or four genes and very few related sequences for the small nuclear U1 RNA. These genes were localized by in situ hybridization at different chromosomal loci and show no spatial relationship to the U2 snRNA genes.     

Transfer RNA genes of Drosophila melanogaster.

Three recombinant plasmids containing randomly sheared genomic D. melanogaster tRNAs have been identified and characterized in detail. One of these, the plasmid 14C4, has a D. melanogaster (Dm) DNA segment of 18 kb, and has three tRNA2Arg and two tRNAAsN genes. The second plasmid, 38B10, has tRNAHis genes, while the third plasmid, 63H5, contains coding sequences for tRNA2Asp. The Dm DNA segments in each recombinant plasmid are derived from unique cytogenetic loci. 14C4 is from 84 F, 38B10 is from 48 F and 63H5 is from 70 A.     

Two new Y-linked genes in Drosophila melanogaster

The Y chromosome and other heterochromatic regions present special challenges for genome sequencing and for the annotation of genes. Here we describe two new genes (ARY and WDY) on the Drosophila melanogaster Y, bringing its number of known single-copy genes to 12. WDY may correspond to the fertility factor kl-1.     

Functional interactions of neurogenic genes of Drosophila melanogaster

The neurogenic genes of Drosophila melanogaster are involved in the decision of ectodermal cells to take on a neural or an epidermal fate. We present evidence in support of the notion that six of the neurogenic genes are functionally related. We studied the phenotype of embryos lacking one of the neurogenic genes in the presence of an increased dosage of the wild-type allele of another neurogenic gene. Our analysis also included the Hairless locus, whose function is related to that of the neurogenic genes, as well as to many other genes. The effects observed were asymmetric in that triploidy for a given gene modified the phenotype of loss of the function of another gene, but triploidy of the latter gene did not modify the phenotype of loss of the function of the former gene. These asymmetries allowed us to establish a polarity of gene interactions, as well as to order the genes according to the assumed ability of some of them to modify the activity of others. In this sequence, almondex is the first link and Enhancer of split the last one. Our evidence suggests that the function of big brain is independent of the function of the other six. The consequences of this arrangement for the commitment of ectodermal cells are discussed.     

Characterization and expression of collagen-like genes in Drosophila melanogaster

We have used a cloned chicken collagen cDNA sequence to help identify hypothetic members of the collagen gene family from Drosophila melanogaster. Several experimental evidences have been obtained which indicate that the Drosophila genome contains numerous collagen-like sequences. We have characterized in more detail ten distinct DNA sequences that hybridized strongly to the heterologous collagen probe. By in situ hybridization we have shown that these sequences are dispersed throughout the Drosophila genome. Two of them are shown to originate from the previously described DCg 1 and DCg 2 collagen genes. In other respects, we show that in addition to DCg 1 and DCg 2, at least five putative collagen genes are expressed during the Drosophila lifetime. These genes are unique, and some of them are seen to be transcribed into different size classes of mRNAs. Additionally, the data presented so far demonstrate that the expression of these genes is regulated temporally and/or quantitatively during the Drosophila life cycle.     

Organization of the ferritin genes in Drosophila melanogaster

The organization of two closely clustered genes, Fer1HCH and Fer2LCH, encoding the heavy-chain homolog (HCH) and the light-chain homolog (LCH) subunits of Drosophila melanogaster ferritin are reported here. The 5019-bp sequence of the cluster was assembled from genomic fragments obtained by polymerase chain reaction (PCR) amplification of genomic DNA and from sequences obtained from the Berkeley Drosophila Genome Project (BDGP) (http://www.fruitfly.org). These genes, located at position 99F1, have different exon-intron structures (Fer1HCH has three introns and Fer2LCH has two introns) and are divergently transcribed. Computer analysis of the possibly shared promoter regions revealed the presence of putative metal regulatory elements (MREs), a finding consistent with the upregulation of these genes by iron, and putative NF-kappaB-like binding sites. The structure of two other invertebrate ferritin genes, from the nematode Caenorhabditis elegans (located on chromosomes I and V), was also analyzed. Both nematode genes have two introns, lack iron-responsive elements (IREs), and encode ferritin subunits similar to vertebrate H chains. These findings, along with comparisons of ferritin genes from invertebrates, vertebrates, and plants, suggest that the specialization of ferritin H and L type chains, the complex exon-intron organization of plant and vertebrate genes, and the use of the IRE/iron regulatory protein (IRP) mechanism for regulation of ferritin synthesis are recent evolutionary acquisitions.     

Isolation of developmentally regulated genes in Drosophila melanogaster

We used a molecular approach to search for maternally expressed genes in Drosophila melanogaster. The relative merits of differential and competition screens were analyzed in a series of reconstruction experiments using either purified phage plaques or derivative DNA sequences. In the course of this study, we isolated 5 clones whose RNA level varies during early embryogenesis. Three gastrula differential clones, b4, b8 and d3, are present in numerous copies in the genome; clone b4 hybridizes with the copia-like B104 repetitive sequence described by Scherer et al. We also isolated 2 maternally-expressed genes, not previously identified in either classical genetic or similarly molecular-based screens. These clones, b11 and d6, map at cytogenetic positions 98F and 4F respectively, on the polytene chromosome map.     

The 5S genes of Drosophila melanogaster.

We have cloned embryonic Drosophila DNA using the poly (dA-DT) connector method (Lobban and Kaiser, 1973) and the ampicillin-resistant plasmid pSF2124 (So, Gill and Falkow, 1975) as a cloning vehicle. Two clones, containing hybrid plasmids with sequences complementary to a 5S RNA probe isolated from Drosophila tissue culture cells, were identified by the Grunstein and Hogness (1975) colony hybridization procedure. One hybrid plasmid has a Drosophila insert which is comprised solely of tandem repeats of the 5S gene plus spacer sequences. The other plasmid contains an insert which has about 20 tandem 5S repeat units plus an additional 4 kilobases of adjacent sequences. The size of the 5S repeat unit was determined by gel electrophoresis and was found to be approximately 375 base pairs. We present a restriction map of both plasmids, and a detailed map of of the5S repeat unit. The 5S repat unit shows slight length and sequence heterogeneity. We present evidence suggesting that the 5S genes in Drosophila melanogaster may be arranged in a single continuous cluster.