Y chromosomal DNA of Drosophila hydei

Six recombinant DNA clones are described, which are derived from the Y chromosome of Drosophila hydei. They reveal characteristic features of Y chromosomal DNA sequences. Three of the cloned inserts are Y-specific and are members of the same family of repeated sequences associated with the lampbrush loop-forming fertility gene "nooses" in the short arm of the Y chromosome. The other three cloned sequences are members of three different families of repeated sequences, but display a small amount of homology to one another and to the family of the nooses sequences. These three cloned sequences are found preferentially in the Y chromosome, but also in other chromosomal positions. The Y chromosomal copies are located in the short arm of the Y chromosome. The other copies are found in autosomal kinetochore-associated heterochromatin or, for one of the cloned sequences, in one band of the giant chromosome 4, in addition to the kinetochore heterochromatin.     

Selection of DNA sequences from interval 6 of the human Y chromosome with homology to a Y chromosomal fertility gene sequence of Drosophila hydei

Summary An experimental approach towards the molecular analysis of the male fertility function, located in interval 6 of the human Y chromosome, is presented. This approach is not based on the knowledge of any gene product but on the assumption that the functional DNA structure of male fertility genes, evolutionary conserved with their position on the Y chromosome, may contain an evolutionary conserved frame structure or at least conserved sequence elements. We tested this hypothesis by using dhMiF1, a fertility gene sequence of the Y chromosome of Drosophila hydei, as a screening probe on a pool of cloned human Y-DNA sequences. We were able to select 10 human Y-DNA sequences of which 7 could be mapped to Y interval 6 (the pY6H sequence family). Since the only fertility gene of the human Y chromosome is mapped to the same Y interval, our working hypothesis seems to be strongly supported. Most interesting in this respect is the isolation of the Y-specific repetitive pY6H65 sequence. The pY6H65 locus extends to a length of at least 300 kb in Y interval 6 and has a locus-specific repetitive sequence organization, reminiscent of the functional DNA structure of Y chromosomal fertility genes of Drosophila. We identified the simple sequence family (CA)_n as one sequence element conserved between the Drosophila dhMiFi fertility gene sequence and the homologous human Y-DNA sequences.     

Genome analysis: More Drosophila Y chromosome genes

The Drosophila melanogaster Y chromosome has long been known to contain few functional genes other than several required for male fertility. The D. melanogaster genome sequence has now allowed characterization of two more male fertility genes, shedding light on the function and evolution of Y chromosomes.     

Evolution of Y chromosomal lampbrush loop DNA sequences of Drosophila

The evolutionary conservation of Y chromosomal DNA sequences of Drosophila hydei in different species of the genus Drosophila was studied by in situ hybridization and on genomic DNA blots of restriction enzyme digested DNA. We demonstrated that Y specific DNA sequences, which form major parts of lampbrush loops related to the male fertility genes, are only retained in a few closely related species during evolution. Other Y chromosomal DNA sequences, also present in lampbrush loops but with homology to autosomal and X chromosomal locations, were found in distant species. We propose a model for the evolution of the Y chromosomal lampbrush loops.     

Drosophila resistance genes to parasitoids: chromosomal location and linkage analysis

Insect hosts can survive infection by parasitoids using the encapsulation phenomenon. In Drosophila melanogaster the abilities to encapsulate the wasp species Leptopilina boulardi and Asobara tabida each involve one major gene. Both resistance genes have been precisely localized on the second chromosome, 35 centimorgans apart. This result clearly demonstrates the involvement of at least two separate genetic systems in Drosophila resistance to parasitoid wasps. The resistance genes to L. boulardi and A. tabida are not clustered as opposed to many plant resistance genes to pathogens cloned to date.     

Isolation and chromosomal localization of ecdysterone-responsive genes in a Drosophila cell line

Cultured Kc 0% cells of Drosophila melanogaster are responsive to ecdysterone treatment. A library of lambda phages carrying segments of Drosophila genomic DNA was differential screened using poly(A)⁺RNAs from control and ecdysterone-treated cells. Nine independent recombinant phages that hybridized more intensely with poly(A)⁺ RNA from treated cells and six that hybridized most strongly with poly(A)⁺RNA from untreated cells were selected. Genomic localization of these inducible and repressible sequences was determined by hybridization in situ. These results suggest that expression of several unique genes is increased by the hormone. The six repressible sequences each contained DNA that hybridized to multiple chromosomal sites and appeared to be mobile elements, suggesting that the steroid hormone might be acting on the transposable elements. These probes will be useful for the study of positive and negative steroid regulation within the same cell.     

Prenyl proteins in eukaryotic cells: a new type of membrane anchor

Recent studies have indicated that eukaryotic cells contain proteins that are post-translationally modified by long-chain, thioether-linked prenyl groups. These proteins include yeast mating factors, ras proteins and nuclear lamins. The modification occurs on a cysteine residue near the C terminus and appears to initiate a set of additional protein modification reactions that promote attachment of the proteins to specific membranes.     

X and Y chromosomal ribosomal DNA of Drosophila: comparison of spacers and insertions.

In Drosophila melanogaster, the genes coding for 18S and 28S ribosomal RNA (rDNA) are clustered at one locus each on the X and the Y chromosomes. We have compared the structure of rDNA at the two loci. The 18S and 28S rRNAs coded by the X and Y chromosomes are very similar and probably identical (Maden and Tartof, 1974). In D. melanogaster, many rDNA repeating units are interrupted in the 28S RNA sequence by a DNA region called the insertion. There are at least two sequence types of insertions. Type 1 insertions include the most abundant 5 kilobase (kb) class and homologous small (0.5 and 1 kb) insertions. Most insertions between 1.5 and 4 kb have no homology to the 5 kb class and are identified as type 2 insertions. In X rDNA, about 49% of all rDNA repeats have type 1 insertions, and another 16% have type 2 insertions. On the Y chromosome, only 16% of all rDNA repeats are interrupted, and most if not all insertions are of type 2.rDNA fragments derived from the X and Y chromosomes have been cloned in E. coli. The homology between the nontranscribed spacers in X and Y rDNA was studied with cloned fragments. Stable heteroduplexes were found which showed that these regions on the two chromosomes are very similar.The evolution of rDNA in D. melanogaster might involve genetic exchange between the X and Y chromosomal clusters with restrictions on the movement of type 1 insertions to the Y chromosome.     

Ribosomal genes not integrated into chromosomal DNA in Drosophila melanogaster

DNA obtained by a gentle lysis procedure from adult Drosophila melanogaster was analyzed by sucrose gradient sedimentation. The major portion of the DNA has an estimated weight of at least 5–10×10⁹ daltons. All of the ribosomal genes are present in this high molecular weight DNA in adult males with one nucleolus organizer or in adult females with two nucleolus organizers as shown by hybridizing fractions of the gradient with ribosomal RNA. In female adults with one nucleolus organizer instead of the usual two, 68% of the ribosomal genes are found in high molecular weight DNA and 32% are found in DNA of smaller size (3×10⁸ daltons). We propose that these latter genes are not integrated into the DNA of the chromosome.     

Monoclonal antibodies against a specific nonhistone chromosomal protein of Drosophila associated with active genes

Hybridomas secreting monoclonal antibodies have been produced by fusion of NS-1 mouse myeloma cells with the spleen cells of mice inoculated with a 60-65,000-mol wt fraction of proteins released from Drosophila embryo nuclei treated with DNase I. The antibodies secreted by the hybridomas were examined with polytene chromosomes of formaldehyde- fixed salivary gland squashes by an immunofluorescence assay. Most of the clonal antibodies obtained resulted in specific staining of the chromosomes relative to the cytoplasmic debris. In the case of clone 28, the antibodies showed a preferential association with sites of gene activity, both puffs and loci identified as puffing at some time during the third instar and prepupal period. In larvae that were heat shocked (exposed to 35 degrees C for 15 min before removal and fixation of the glands), the antibodies of clone 28 stained preferentially the induced heat-shock loci while continuing to stain most of the normal set of loci. The antigen for clone 28 was identified as a single protein of approximately 62,000 mol wt by using the antibodies followed by 125I- rabbit anti-mouse Ig to stain nitrocellulose replicas of SDS polyacrylamide gels of total chromosomal proteins. This study demonstrates that monoclonal antibodies can be used successfully in immunofluorescence staining of formaldehyde-fixed polytene chromosomes. The results verify the hypothesis that a specific nonhistone chromosomal protein is preferentially associated with the set of loci that includes both active sites and those scheduled to be active at some time in this developmental program. Such proteins may play a general role in the mechanisms of cell determination and gene activation.     

Involvement of Y chromosomal loci in the synthesis of Drosophila hydei sperm proteins

A comparative study of the protein patterns in testes of wild-type and X/O flies of Drosophila hydei revealed quantitative differences in at least three major protein fractions. One protein component of a Mr 155,000 fraction and a protein of Mr 35,000 are completely absent in X/O testes. The amount of protein in a Mr 55,000 fraction is considerably reduced. The tubulins, which are part of this fraction, are also reduced in amount. All three proteins were found as constituents of sperm tails. Studies of Y chromosomal mutants revealed that the presence of at least two of these proteins depends on the activity of loci O, P, and Q of the Y chromosome. However, preliminary evidence indicates an autosomal location of the genes of these sperm proteins. This suggests a regulatory role of Y chromosomal genes in the production of some major sperm proteins.     

A new type of inversion of a human Y chromosome

Summary Using chromosome banding techniques, a phenotypically normal male was found to have an abnormal banding pattern of the Y chromosome. By the constitutive heterochromatin staining method, a darkly stained band was located on the short arm and the proximal region of the long arm. The quinacrine staining method also showed a similar abnormal banding pattern: a brightly fluorescing band was seen on the short arm and the proximal region of the long arm. By the conventional Giemsa staining method, however, no specific morphological abnormality was detected in the aberrant Y. On detailed karyotype analyses no recognizable abnormality of banding patterns of any other chromosome was found aside from the abnormal Y. The abnormality was determined to be a complex inversion of the Y chromosome, which is described as 46,X,inv(Y)(pterp11::q11q12::cen::q12qter).