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Biomedical subjects

A M Mazo

Publications and source records attributed to A M Mazo.

At least 19 recordsLinked to original sources
PubMed1991

Cloning and analysis of the mobile element gypsy from D. virilis.

The homologue of the Drosophila melanogaster mobile element gypsy was cloned from the distantly related species D. virilis. It has three ORFs highly homologous to those of the element from D. melanogaster. gypsy from D. virilis appears to be actively transcribed and is capable of transposition. Comparison of the untranslated regions of both elements revealed conserved sequences including those which had previously been demonstrated to be important in transcription regulation. Distribution of gypsy among the different strains of D. virilis and different species within the D. virilis group was analyzed. Possible involvement of horizontal transmission in the process of spreading and evolution of gypsy is discussed.

Animals↗
PubMed1990

Evidence for horizontal transmission of the mobile element jockey between distant Drosophila species.

We addressed the possibility of the horizontal transfer of long interspersed element (LINE)-like mobile elements by studying the distribution of the Drosophila melanogaster LINE-like element jockey in different Drosophila species. Outside the D. melanogaster group jockey was detected only in the distantly related species Drosophila funebris. Cloning and sequencing of this element from D. funebris revealed the existence of the two open reading frames highly similar to those of jockey from D. melanogaster. Elements from both species are transcriptionally active and contain in their promoter regions a conserved sequence important for its activity. The high degree of similarity between the D. melanogaster and the D. funebris jockey and the absence of jockey from other sibling species of the D. funebris group provide evidence for the horizontal transmission of jockey into D. funebris.

Amino Acid Sequence↗
PubMed1990

The trithorax gene, a trans-acting regulator of the bithorax complex in Drosophila, encodes a protein with zinc-binding domains.

The trithorax (trx) gene functions in segment determination in Drosophila through interaction with genes of the bithorax complex and Antennapedia complex. Genetic evidence suggests that trx may be considered a positive regulator of homeotic genes. Sequencing of cDNAs corresponding to the entire trx transcription unit revealed the existence of an unusually long open reading frame encoding 3759 amino acids. The main features of the predicted trx protein are several cysteine-rich regions which can be folded into zinc finger-like domains. Cysteine-rich portions expressed from trx cDNAs in Escherichia coli are capable of zinc binding in vitro, suggesting a possible function for the trx product as a metal-dependent DNA-binding protein. Analysis of trx mutant embryos with antibody to the Ultrabithorax (Ubx) gene product showed decreased staining in parasegment 6 of the ventral nerve cord of late embryos. However, expression of Ubx was not affected in embryos carrying the lethal mutation trxE3, in which one of the putative zinc finger-like domains of the trx protein is deleted. This differential effect of the E3 mutation suggests that trx exhibits other function(s) besides those involved in the regulation of Ubx expression in the ventral nerve cord of the embryo.

Amino Acid Sequence↗
PubMed1989

Suppression in Drosophila: su(Hw) and su(f) gene products interact with a region of gypsy (mdg4) regulating its transcriptional activity.

The gypsy (mdg4) mobile element of Drosophila contains two closely spaced regions which bind proteins from nuclear extracts. One of these is an imperfect palindrome having homology with the lac-operator of Escherichia coli; the other contains a reiterated sequence (5'PyPuT/C TGCATAC/TPyPy) homologous to the octamer that is the core of many enhancers and upstream promoter elements. Transient expression of deletion mutants has shown that these DNA regions are negative and positive regulators of transcription. As was demonstrated earlier by other authors, mutations induced by the presence of gypsy in different loci are suppressed owing to either repression or activation of gypsy transcription in Drosophila strains carrying unlinked mutations in su(Hw) or su(f) genes. We have shown that binding to a negative regulator (silencer) is weakened in nuclear extracts isolated from fly stocks carrying su(f) mutations which activate gypsy transcription; therefore the su(f) gene seems to code for a protein capable of gypsy repression. Furthermore, binding to a positive regulator is weakened in nuclear extracts isolated from fly stocks carrying su(Hw) gene mutations which decrease the level of gypsy transcription; therefore, the su(Hw) gene most likely encodes a protein which activates gypsy transcription.

Animals↗
PubMed1989

Murine muscle-specific enolase: cDNA cloning, sequence, and developmental expression.

In vertebrates, the glycolytic enzyme enolase (EC 4.2.1.11) is present as homodimers and heterodimers formed from three distinct subunits of identical molecular weight, alpha, beta, and gamma. We report the cloning and sequencing of a cDNA encoding the beta subunit of murine muscle-specific enolase. The corresponding amino acid sequence shows greater than 80% homology with the beta subunit from chicken obtained by protein sequencing and with alpha and gamma subunits from rat and mouse deduced from cloned cDNAs. In contrast, there is no homology between the 3' untranslated regions of mouse alpha, beta, and gamma enolase mRNAs, which also differ greatly in length. The short 3' untranslated region of beta enolase mRNA accounts for its distinct length, 1600 bases. It is known that a progressive transition from alpha alpha to beta beta enolase occurs in developing skeletal muscle. We show that this transition mainly results from a differential regulation of alpha and beta mRNA levels. Analysis of myogenic cell lines shows that beta enolase gene is expressed at the myoblast stage. Moreover, transfection of premyogenic C3H10T1/2 cells with MyoD1 cDNA shows that the initial expression of beta transcripts occurs during the very first steps of the myogenic pathway, suggesting that it could be a marker event of myogenic lineage determination.

Actins↗
PubMed1989

[Interaction of products of su(Hw) and su(f) genes with MDG4 region regulating its transcription suppresses mutations in Drosophila caused by insertion of this gene].

The mdg4 (gypsy) mobile element of Drosophila contains two closely situated regions binding to proteins from nuclear extracts. One of these is an imperfect palindrome having homology with the lac operator of Escherichia coli, the other contains a reiterated sequence (5'PyPuTCTGCATACTPyPy) homologous to the octamer which is the core of many enhancers and upstream promoter elements. The transient expression of deletion mutants has shown that these DNA regions are negative and positive regulators, respectively, of mdg4 transcription. As was demonstrated earlier, mutations induced by the presence of mdg4 at different loci are suppressed, owing to either repression or activation of mdg4 transcription in Drosophila lines carrying unlinked mutations in su(Hw) or su(f) genes. We have shown that binding to a negative regulator (silencer) is weakened in nuclear extracts isolated from cell lines carrying su(f) mutations which activate mdg4 transcription; therefore, the su(f) gene codes for a protein capable of mdg4 repression. Furthermore, binding to a positive regulator is weakened in nuclear extracts isolated from cell lines carrying su(Hw) gene mutations which decrease the level of mdg4 transcription; hence, the su(Hw) gene encodes a protein which activates mdg4 transcription.

Animals↗
PubMed1986

Nucleoside 5'-triphosphates modified at sugar residues as substrates for calf thymus terminal deoxynucleotidyl transferase and for AMV reverse transcriptase.

Terminal deoxynucleotidyl transferase from calf thymus and RNA-directed DNA polymerase (reverse transcriptase) from the avian myeloblastosis virus catalyze the incorporation of 3'-amino-2',3'-dideoxynucleoside 5'-triphosphates, as well as some of their 3'-derivatives, 3'-amino-3'-deoxyarabinonucleoside 5'-triphosphates and some other nucleoside 5'-triphosphates modified at sugar residues. After incorporation of the appropriate 5'-mononucleotide residue into the DNA, further chain elongation is blocked. This finding opens up a possibility for selective inhibition of DNA synthesis catalyzed by a certain enzyme.

Animals↗
PubMed1986

The steps of reverse transcription of Drosophila mobile dispersed genetic elements and U3-R-U5 structure of their LTRs.

Reverse transcription intermediate forms (minus and plus strong-stop DNA) are detected in Drosophila melanogaster cultured cells for mobile dispersed genetic elements mdg1, mdg3, and mdg4 (gypsy). The mdg elements studied possess a common mechanism of reverse transcription, despite their structural differences, and the comparative analysis of intermediate forms proves that mdg elements pass the same stages of reverse transcription as retroviruses. The length of minus strong-stop DNA that locates the RNA start site coincides with the data obtained from S1 nuclease analysis of transcription initiation. S1 analysis has also revealed that mdg LTRs have a U3-R-U5 structure analogous to that of retroviral LTRs. Transcription of mdg1, mdg3, and mdg4 is initiated within or immediately after the same sequence TCAGTPy. Neither the TATA box nor the CAAT box can be found at their characteristic positions upstream of the 5' ends of mRNAs.

Animals↗
PubMed1986

[Fine structure of long terminal repeats and stages of reverse transcription of mobile dispersed genes in Drosophila].

In Drosophila melanogaster cultured cells, RNA reverse transcription intermediate forms connected with initiation of minus and plus DNA strand synthesis (minus and plus strong-stop DNA) are detected for mobile dispersed genetic elements MDG1, MDG3 and MDG4 (gypsy). A comparative analysis of intermediate forms has proved that mdg elements pass the same stages of reverse transcription as retroviruses, revealing a complete similarity between intermediate products. It has also been established that these three mdg elements possess a common mechanism of reverse transcription, despite their structural differences. The length of the minus strong-stop DNA, that gives the position of the RNA start site, coincides with the data obtained from SI nuclease analysis of transcription initiation. SI mapping has also revealed that mdg RNA carries a repeated sequence R on its ends, similar to retroviral RNA molecules, and that mdg LTRs have a U3-R-U5 structure analogous to that of proretroviral LTRs. Transcription of mdg1, mdg3 and mdg4 is initiated within or immediately after the same sequence TCAGTPy. Neither TATA box nor CAAT box can be found in their characteristic positions upstream of the 5' ends of mRNA.

Animals↗
PubMed1986

[Structure of long terminal repeats of transcriptionally active and inactive copies of the mobile dispersed gene MDG3 in Drosophila melanogaster].

The nucleotide sequences of long terminal repeats (LTRs) and adjacent regions are determined in the transcribed and non-transcribed variants of a mobile dispersed genetic element MDG3. MDG3 is similar to other mdg elements. A 4 bp duplication of the host DNA is generated upon its integration. MDG3 is flanked by a 5 bp inverted repeat. The length of the LTRs varies in different MDG3 variants, the difference being connected mainly with duplications of certain sequences in U3 and R regions. The copies with 267 bp LTR are the most abundant ones and perfectly conservative in their primary structure. They are transcribed in 67J25D cell culture and are not transcribed in Kc cell line, where another variant with LTR length 293 bp is transcriptionally active. S1-mapping of transcription initiation and termination sites has demonstrated that in both MDG3 variants they are situated in the same positions, and the LTR itself may be subdivided into U3, R and U5 regions, like retroviral LTRs. Possible factors involved in the regulation of mdg transcription are discussed.

Animals↗
PubMed1984

The secondary structure of oocyte and somatic 5S ribosomal RNAs of the fish Misgurnus fossilis L. from nuclease hydrolyses and chemical modification data.

We have studied the accessibility of 5'- 32P labeled oocyte and somatic 5S rRNAs from the fish Misgurnus fossilis L. to S1, T1 and cobra venom nucleases and have found that the cleavage sites of 5S rRNAs closely related in primary structures differ in these molecules. The data of nuclease hydrolyses revealed the existence of two conformers corresponding to renatured and partially denatured somatic 5S rRNA and capable of mutual interconversions. The exposed cytosine residues were located in oocyte and somatic 5S rRNAs converted into uridine ones by sodium bisulfite treatment. The data have been used to construct the secondary structure models of somatic and oocyte 5S rRNAs by means of specially devised computer program. These models differ in their 5'-halves which contain all the nucleotide substitutions in the primary structure, all differences in location of the exposed cytosine residues, and finally, in the cleavage pattern by the nucleases used.

Animals↗
PubMed1983

Discrete poly(A)- RNA species from rat liver mitochondria are fragments of 16S mitochondrial rRNA carrying its 5'-termini.

During electrophoresis in polyacrylamide gels containing 7M urea the major discrete components of preparations of rat liver mitochondrial poly(A)+ and poly(A)- RNA species have similar mobilities. Poly(A)- RNA components hybridize to the 16S rRNA gene of mtDNA. Analysis of 5'-terminal sequences of these components revealed their identity to the 5'-terminal sequence of 16S rRNA. These results show that poly(A)- RNA components are fragmentation products of 16S rRNA. Fragmentation occurs nonrandomly from the 3'-end of the original rRNA molecules and lead to formation of products with electrophoretic mobilities similar to those of poly(A)+ RNA components.

Animals↗
PubMed1983

Transcriptional mapping of the rat liver mitochondrial genome.

We have identified and mapped nine discrete poly(A)-containing RNAs (RNA-2 to RNA-10) transcribed from rat liver mitochondrial DNA. The 5'-terminal fragments have been sequenced in five of these. The transcriptional map of rat mitochondrial DNA is homologous to those for mitochondrial DNAs of man and mice. The 5'-terminal nucleotide sequences of poly(A)-containing RNAs from rat liver mitochondria are similar in structure to those of HeLa cells studied by other authors; none of them have leader sequences.

Animals↗
PubMed1981

The primary structure of oocyte and somatic 5S rRNAs from the loach Misgurnus fossilis.

Somatic and oocyte 5S rRNAs from the liver and unfertilized eggs of the loach (Misgurnus fossilis have been sequenced and found to differ in six nucleotides. All the substitutions are confined to the 5'-half of the molecules; 4 of them are pyrimidine-pyrimidine substitutions, and 2 are purine-pyrimidine ones. Considerable differences, both in the position and the character of substitutions, have been established when these 5S rRNAs were compared with somatic and oocyte 5S rRNAs from Xenopus borealis and Xenopus laevis. Among the known primary structures, somatic 5S rRNA of M. fossilis is most similar to trout 5S rRNA.

Animals↗
PubMed1980

A rapid method for mapping exposed cytosines in polyribonucleotides. Application to tRNATrp (yeast, beef liver).

A rapid method for mapping exposed cytosine residues in 5'-[32P]-labeled RNA molecules is suggested. The exposed cytosines (C's) are converted into uracyls (U's) by bisulphite treatment at pH 5.8 in the presence of Mg2+, followed by complete modification of the residual (non-exposed) C's by a methoxyamine and bisulphite mixture at pH 5.0. The control RNA is modified only by methoxyamine and bisulphite without the preliminary C leads to U conversion. The location of the exposed C's is determined by comparing the products of partial T1, T2, A and U2 ribonuclease digestions of the C leads to U converted and control RNAs after slab gel polyacrylamide electrophoresis and autoradiography. The method has been applied for mapping exposed cytosine bases in tRNATrp (yeast) which have been found in the anti-codon loop and at the 3'-end of the molecule. In tRNATrp (beef liver), in addition to the same exposed bases, C in the diHU-loop is exposed. The data obtained are in full agreement with what is known about exposed C's for other tRNAs.

Animals↗
PubMed1979

An improved rapid enzymatic method of RNA sequencing using chemical modification.

A version of rapid gel sequencing procedure based on the analysis of partial endonuclease hydrolizates of chemically modified 5'-32P-labelled RNA is suggested. Complete and selective modification of cytidilic residues by a methoxyamine-bisulfite mixture leads to the unfolding of the RNA secondary structure and, due to this effect, to the generation of a more uniform set of fragments after partial RNAase hydrolysis. The position of cytidines in an RNA sequence can be determined by restricting the hydrolysis of phosphodiester bonds between the modified CMP residues and their 3'-neighbours with T2 and A RNAases. The method was verified with tRNATrp (yeast) and 5S RNA (rat liver and yeast).

Animals↗