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M Simonelig

Publications and source records attributed to M Simonelig.

12 recordsLinked to original sources
PubMed2000

Tissue-specific autoregulation of Drosophila suppressor of forked by alternative poly(A) site utilization leads to accumulation of the suppressor of forked protein in mitotically active cells.

The Suppressor of forked protein is the Drosophila homolog of the 77K subunit of human cleavage stimulation factor, a complex required for the first step of the mRNA 3'-end-processing reaction. We have shown previously that wild-type su(f) function is required for the accumulation of a truncated su(f) transcript polyadenylated in intron 4 of the gene. This led us to propose a model in which the Su(f) protein would negatively regulate its own accumulation by stimulating 3'-end formation of this truncated su(f) RNA. In this article, we demonstrate this model and show that su(f) autoregulation is tissue specific. The Su(f) protein accumulates at a high level in dividing tissues, but not in nondividing tissues. We show that this distribution of the Su(f) protein results from stimulation by Su(f) of the tissue-specific utilization of the su(f) intronic poly(A) site, leading to the accumulation of the truncated su(f) transcript in nondividing tissues. Utilization of this intronic poly(A) site is affected in a su(f) mutant and restored in the mutant with a transgene encoding wild-type Su(f) protein. These data provide an in vivo example of cell-type-specific regulation of a protein level by poly(A) site choice, and confirm the role of Su(f) in regulation of poly(A) site utilization.

Animals↗
PubMed1999

The Drosophila poly(A)-binding protein II is ubiquitous throughout Drosophila development and has the same function in mRNA polyadenylation as its bovine homolog in vitro.

The poly(A)-binding protein II (PABP2) is one of the polyadenylation factors required for proper 3'-end formation of mammalian mRNAs. We have cloned Pabp2, the gene encoding the Drosophila homolog of mammalian PABP2, by using a molecular screen to identify new Drosophila proteins with RNP-type RNA-binding domains. Sequence comparison of PABP2 from Drosophila and mammals indicates that the most conserved domains are the RNA-binding domain and a coiled-coil like domain which could be involved in protein-protein interactions. Pabp2 produces four mRNAs which result from utilization of alternative poly(A) sites and encode the same protein. Using an antibody raised against Drosophila PABP2, we show that the protein accumulates in nuclei of all transcriptionally active cells throughout Drosophila development. This is consistent with a general role of PABP2 in mRNA polyadenylation. Analysis of Drosophila PABP2 function in a reconstituted mammalian polyadenylation system shows that the protein has the same functions as its bovine homolog in vitro : it stimulates poly(A) polymerase and is able to control poly(A) tail length.

Amino Acid Sequence↗
PubMed1999

The suppressor of forked gene of Drosophila, which encodes a homologue of human CstF-77K involved in mRNA 3'-end processing, is required for progression through mitosis.

The Suppressor of forked (Su(f)) protein of Drosophila melanogaster is a homologue of the 77K subunit of human cleavage stimulation factor required for cleavage of pre-mRNAs before addition of poly(A). We have previously shown that the Su(f) protein is not ubiquitously distributed: it accumulates in dividing cells at various stages of Drosophila development. In this paper, we show that phenotypes of su(f) temperature-sensitive mutants result from a defect in cell proliferation. Analysis of the mitotic phenotype of su(f) temperature-sensitive alleles in larval brain and in imaginal discs reveals an increase in the number of metaphases with overcondensed chromosomes and asymmetric or reduced mitotic spindles. In contrast, neural differentiation in eye imaginal discs of the same mutant flies does not appear to be affected. These results indicate that su(f) is required during cell division for progression through metaphase. Taken together, these data suggest that a decrease in su(f) activity preferentially affects 3'-end formation of particular mRNAs, some of which are involved in mitosis, and are in agreement with a role of su(f) in the regulation of poly(A) site utilization.

Animals↗
PubMed1998

Autoregulation at the level of mRNA 3' end formation of the suppressor of forked gene of Drosophila melanogaster is conserved in Drosophila virilis.

The Drosophila melanogaster Suppressor of forked [Su(f)] protein shares homology with the yeast RNA14 protein and the 77-kDa subunit of human cleavage stimulation factor, which are proteins involved in mRNA 3' end formation. This suggests a role for Su(f) in mRNA 3' end formation in Drosophila. The su(f) gene produces three transcripts; two of them are polyadenylated at the end of the transcription unit, and one is a truncated transcript, polyadenylated in intron 4. Using temperature-sensitive su(f) mutants, we show that accumulation of the truncated transcript requires wild-type Su(f) protein. This suggests that the Su(f) protein autoregulates negatively its accumulation by stimulating 3' end formation of the truncated su(f) RNA. Cloning of su(f) from Drosophila virilis and analysis of its RNA profile suggest that su(f) autoregulation is conserved in this species. Sequence comparison between su(f) from both species allows us to point out three conserved regions in intron 4 downstream of the truncated RNA poly(A) site. These conserved regions include the GU-rich downstream sequence involved in poly(A) site definition. Using transgenes truncated within intron 4, we show that sequence up to the conserved GU-rich domain is sufficient for production of the truncated RNA and for regulation of this production by su(f). Our results indicate a role of su(f) in the regulation of poly(A) site utilization and an important role of the GU-rich sequence for this regulation to occur.

Amino Acid Sequence↗
PubMed1998

The suppressor of forked protein of Drosophila, a homologue of the human 77K protein required for mRNA 3'-end formation, accumulates in mitotically-active cells.

The suppressor of forked (Su(f)) protein of Drosophila melanogaster is highly homologous to two proteins involved in mRNA 3'-end formation, the yeast RNA14 protein and the 77K subunit of human cleavage stimulation factor (CstF). This suggests a role for su(f) in mRNA 3'-end-processing, probably as part of Drosophila CstF. We have investigated the expression pattern of su(f) during Drosophila development and found that the su(f) gene product is not detected ubiquitously. The Su(f) protein accumulates in mitotically-active cells, but does not in non-dividing cells. This expression pattern corroborates earlier data suggesting that the phenotypes of su(f) mutants could result from a defect in cell proliferation. Our results suggest that, in Drosophila, Su(f) is involved in the regulatory function of CstF.

Animals↗
PubMed1996

Interallelic complementation at the suppressor of forked locus of Drosophila reveals complementation between suppressor of forked proteins mutated in different regions.

The Su(f) protein of Drosophila melanogaster shares extensive homologies with proteins from yeast (RNA14) and man (77 kD subunit of cleavage stimulation factor) that are required for 3' end processing of mRNA. These homologies suggest that su(f) is involved in mRNA 3' end formation and that some aspects of this process are conserved throughout eukaryotes. We have investigated the genetic and molecular complexity of the su(f) locus. The su(f) gene is transcribed to produce three RNAs and could encode two proteins. Using constructs that contain different parts of the locus, we show that only the larger predicted gene product of 84 kD is required for the wild-type function of su(f). Some lethal alleles of su(f) complement to produce viable combinations. The structures of complementing and noncomplementing su(f) alleles indicate that 84-kD Su(f) proteins mutated in different domains can act in combination for partial su(f) function. Our results suggest protein-protein interaction between or within wild-type Su(f) molecules.

Alleles↗
PubMed1993

Homology with Saccharomyces cerevisiae RNA14 suggests that phenotypic suppression in Drosophila melanogaster by suppressor of forked occurs at the level of RNA stability.

The suppressor of forked [su(f)] locus of Drosophila melanogaster encodes at least one cell-autonomous vital function. Mutations at su(f) can affect the expression of unlinked genes where retroviral-like transposable elements are inserted. Changes in phenotype are correlated with changes in mRNA profiles, indicating that su(f) affects the production and/or stability of mRNAs. We have cloned the su(f) gene by P-element transposon tagging. Alterations in the DNA map of eight lethal alleles were detected in a 4.3-kb region. P-element-mediated transformation using a fragment including this interval rescued all aspects of the su(f) mutant phenotype. The gene is transcribed to produce a major 2.6-kb RNA and minor RNAs of 1.3 and 2.9 kb, which are present throughout development, being most abundant in embryos, pupae, and adult females. The major predicted gene product is an 84- kD protein that is homologous to RNA14 of Saccharomyces cerevisiae, a vital gene where mutation affects mRNA stability. This suggests that phenotypic modification by su(f) occurs at the level of RNA stability.

Amino Acid Sequence↗
PubMed1992

I elements and the Drosophila genome.

LINEs are a large class of transposable elements in eukaryotes. They transpose by reverse transcription of an RNA intermediate. I elements of Drosophila melanogaster belong to this class and are responsible for the I-R system of hybrid dysgenesis. Many results indicate that at the beginning of the century natural populations of this species were devoid of active I elements and that they were invaded by functional I elements in the last decades. Many Drosophila species contain both defective and active I elements. It seems that the latter were lost in Drosophila melanogaster before its spread throughout the world, and that the recent invasion results from the spread of functional elements originating either from another species by horizontal transfer or from an isolated population of the same species. These data are discussed, as well as their significance in evolutionary processes.

Amino Acid Sequence↗
PubMed1991

A P element of Scaptomyza pallida is active in Drosophila melanogaster.

Several results suggest that P elements have recently invaded natural populations of Drosophila melanogaster after a horizontal transfer from another species. The donor species is thought to come from the willistoni group, which contains P elements very homologous to those of D. melanogaster. However, more divergent P elements are present in many other Drosophilidae species. We have analyzed such elements from Scaptomyza pallida, a species phylogenetically distant to D. melanogaster. We report here the isolation of two coding P elements from S. pallida (PS2 and PS18) that are 4% divergent from one another. At least one of these elements (PS18) is active since it is able to transpose in D. melanogaster and to mobilize a D. melanogaster defective P element, even though its nucleotide sequence is 24% divergent from the canonical P element of D. melanogaster. To our knowledge, a P element that is active and strongly divergent from the D. melanogaster P element has not been reported previously. Sequence comparison between the complete P elements of D. melanogaster and S. pallida reveals that the structural characteristics are maintained: PS2 and PS18 contain terminal inverted repeats and internal repeats very similar to those of the D. melanogaster P element. In addition, the noncoding regions cis necessary for the transposition are more conserved than the coding sequences. Two domains found in the D. melanogaster P transposase (helix-turn-helix and leucine zipper) are well conserved in the putative proteins encoded by PS2 and PS18. This study provides insights into which parts of P elements are functionally important and correlates with functional studies of the P element in D. melanogaster.

Amino Acid Sequence↗
PubMed1988

Transposable and nontransposable elements similar to the I factor involved in inducer-reactive (IR) hybrid dysgenesis in Drosophila melanogaster coexist in various Drosophila species.

The I factor is a transposable element controlling inducer-reactive (IR) hybrid dysgenesis in Drosophila melanogaster, which occurs when males from the class of inducer strains are crossed with females from the class of reactive strains. Inducer strains contain several copies of the complete 5.4-kilobase (kb) I factor at various sites on the chromosomal arms; reactive strains contain no complete I factor. Incomplete and defective I elements occur at constant locations in pericentromeric heterochromatin of both types of strains. The 5.4-kb I factors transpose, whereas incomplete I elements do not transpose. The constant location of defective I elements in all strains indicates that they were in the genome before the spread of D. melanogaster throughout the world. Sequences homologous to I occur in other Drosophila species, and their distribution correlates with the phylogenetic relationships between species. We have studied the organization of I homologues in Drosophila simulans and Drosophila teissieri. These species seem to contain both transposable I elements, even though their structure may differ from that of the 5.4-kb I factors of the inducer strains of D. melanogaster, and nontransposable I elements, which are always at the same place in the genome when different stocks of the same species are compared. These results suggest that both mobile and nonmobile I elements are very old components of the Drosophilidae genome.

Animals↗