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E Ullu

Publications and source records attributed to E Ullu.

54 records · Page 3Linked to original sources
PubMed1984

Human genes and pseudogenes for the 7SL RNA component of signal recognition particle.

Of the several hundred 7SL RNA-like sequences that are dispersed in human DNA, no more than four are likely to represent genes for 7SL RNA; the majority are 7SL pseudogenes which appear to result from the reverse flow of genetic information from 7SL RNA back into genomic DNA. We present the sequence of five 7SL pseudogenes displaying an unprecedented diversity of structures. All are truncated copies of 7SL RNA, but the site of truncation can occur at either the 5' end, the 3' end or at both ends of the RNA sequence. We suggest that such diverse 7SL pseudogenes are generated by different but related pathways. In particular, we argue that two of the loci are secondary 7SL pseudogenes which derive from RNA polymerase III transcripts of primary (preexisting) 7SL pseudogenes. We also report the isolation and characterisation of a human genomic clone carrying two linked 7SL RNA coding regions, 7L30.1 and 7L30.2. The 7L30.2 locus differs by several single base changes from the known human 7SL RNA sequences and does not appear to be expressed at a detectable level in HeLa cells. The 7L30.1 locus is an authentic 7SL RNA gene encoding one of the three sequence variants of human 7SL RNA.

Base Sequence↗
PubMed1984

DNA sequences complementary to human 7 SK RNA show structural similarities to the short mobile elements of the mammalian genome.

A complementary DNA clone of 7 SK RNA from HeLa cells was used to study the genomic organization of 7 SK sequences in the human genome. Genomic hybridizations and genomic clones show that 7 SK is homologous to a family of disperse repeated sequences most of which lack the 3' end of the 7 SK RNA sequence. Only few of the genomic K sequences are homologous to both 3' and 5' 7 SK probes and presumably include the gene(s) for 7 SK RNA. The sequence of four genomic 7 SK clones confirms that they are in most cases pseudogenes. Although Alu sequences are frequently found near the 3' and 5' end of K DNA, the sequences immediately flanking the pseudogenes are different in all clones studied. However, direct repeats were found flanking directly the K DNA or the K-Alu unit, suggesting that the K sequences alone or in conjunction with Alu DNA might constitute a mobile element.

Base Sequence↗
PubMed1982

Cloning and characterization of cDNA copies of the 7S RNAs of HeLa cells.

We have cloned cDNA copies of in vitro adenylated 7S RNA of HeLa cells. The most representative clones in the library contain DNA fragments copied from the 7SL and 7SK small RNAs. The two classes of recombinants share no homology. The 7SL RNA contains at the 5' end of the molecule sequences homologous to the Alu sequence family. Hybridization to human genomic DNA shows that the 7SL and 7SK clones are homologous to two different families of repetitive sequences.

Cloning, Molecular↗
PubMed1982

Human 7SL RNA consists of a 140 nucleotide middle-repetitive sequence inserted in an alu sequence.

We have cloned and sequenced a cDNA copy of in vitro-polyadenylated 7SL RNA of HeLa cells. The cloned fragment is 303 bp long and has a composite structure. A central block of 140 bp is homologous to a new set of human middle-repetitive sequences. This block appears to be inserted in an Alu consensus sequence, 100 bp from the 5' end and 40 bp from the 3' end of the Alu monomer. Two 6 bp direct repeats are found at the junction between the Alu flanking sequences and the central element. The analysis of several clones shows the existence of sequence microheterogeneity in the 5' portion of the molecule. The 7L DNA probably represents a subset of the Alu family of DNA, highly conserved in evolution.

Base Sequence↗
PubMed1979

Construction of a recombinant bacterial plasmid containing DNA sequences for a mouse embryonic globin chain.

Messenger RNAs for mouse embryonic globins were purified from yolk sac derived eyrthroid cells in mouse fetuses. Double stranded DNAs complementary to these messengers were synthesized and blunt end ligated to a EcoRI digested and DNA polymerase I repaired pBR322 plasmid. Of the ampicillin resistant transformants, one contained a plasmid with globin-specific cDNA. The inserted sequence is about 350 base pairs long. It contains one restriction site for EcoRI and one restriction site for HinfI about 170 and 80 base pairs from one end. The insert is not cleaved by HindIII, HindII, BamHI, PstI, SalI, AvaI, TaqI, HpaII, BglI. A mixture of purified messengers coding for alpha chains and for x, y and z embryonic chains was incubated with the recombinant plasmid and the hybridized messenger was translated in a mRNA depleted reticulocyte lysate protein synthesizing system. The product of translation was identified as a z chain by carboxymethylcellulose cromatography. The recombinant plasmid is named "pBR322-egz" after embryonic globin z.

Animals↗
PubMed1979

Nuclear RNA sequences coding for alpha and beta globins in erythroid cells: evidence for multiple intermediate molecules.

The poly (A)-containing nuclear RNA from dimethylsulfoxide-induced Friend leukemia cells was fractionated by acrylamide gel electrophoresis in denaturing conditions and analyzed for alpha and beta globin RNA sequences. The results indicate that nuclear RNA contains one species of large-size RNA (0.6 X 10(6) daltons), which is the putative precursor for beta globin mRNA only. In addition, it was shown by electrophoretic analysis that the complex of RNA molecules not resolved by sucrose gradient centrifugation (11S) comprises sequences of decreasing size (0.34, 0.28, and 0.26 X 10(6) daltons), which might be the precursors of alpha and beta globin mRNA.

Erythrocytes↗
PubMed1978

Isolation and characterization of the messenger RNAs for mouse embryonic globin chains.

Messenger RNAs for mouse embryonic globins were purified from yolk sac erythroid cells by oligodeoxythymidilate-cellulose chromatography and sucrose density centrifugation. Full-sized complementary DNA copies of embryonic globin mRNAs were synthesized. Acrylamide gel electrophoresis of these RNAs indicate an average molecular weight of 220 000, including a polyadenylated sequence of about 35 residues, as determined by hybridization to [3H]polyuridylate. The wheat-germ translation products of mRNAs have the size and the ionic characteristics of the four embryonic globin chains alpha, x, y and z. Hybridization kinetics in vast RNA excess were performed and compared to standard r0t curves of adult globin messengers, demonstrating a total base sequence complexity of about 880 000 daltons, that is four different RNA sequences of 220 000 molecular weight. The titration of embryonic globin cDNAs with increasing amounts of their complementary RNA templates indicates that the embryonic globin messengers were isolated at a high degree of purity.

Animals↗
PubMed1978

Terminal stages of erythroid differentiation: persistent production of globin messenger RNA is necessary to sustain globin synthesis.

The kinetic relationship between the globin mRNA accumulation and the rate of synthesis of globin chains was studied during the terminal stages of differentiation in erythroid cells derived from the yolk sac of mouse fetuses. RNA derived from the whole cells and from different cell compartments were hybridized to DNA complementary to embryonic globin mRNA. The relative proportion of embryonic globin RNA molecules and their absolute number per cell were estimated on the 11th, 12th, and 13th days of mouse fetal development. During erythroid terminal differentiation globin mRNA became progressively predominant on polyribosomes along with the progressive specialization of cell functions. The number of embryonic globin RNA molecules per cell remained constant while yolk sac erythroid cells underwent two rounds of cell division. These data indicate that the transcription of globin genes is operative throughout the last stages of terminal differentiation and that there is no detectable storage of globin RNA sequences in these cells. The rates of accumulation of mRNA molecules and of globin synthesis both seem correlated to the length of the cell cycle.

Animals↗
PubMed1977

Mouse satellite DNA isolated by Ag+ -- CsSO4 density gradients contains G+C rich, slow reassociating sequences.

Mouse satellite DNA sequences isolated by centrifugation in CS2SO4--Ag+ gradients are analyzed for buoyant density by CSCl density gradients and for their content of fast reassociating sequences by denaturation and partial reassociation. Our data suggest that in CS2SO4 gradients silver ions separate a satellite band which contains both fast reassociating G+C rich sequences and slow reassociating, A+T rich DNA sequences.

Animals↗
PubMed1975

Polyribosomal structures inactive for protein synthesis present in erythroid cells during terminal stages of differentiation.

During the terminal stages of differentiation nucleated erythroid cells from the fetal mouse synthesize hemoglobin at a lower rate because after the last cycle of cell division about half of their polyribosomal structures are rendered inactive for protien synthesis though they maintain their aggregated shape. Partially inactive polyribosomes are tested in comparison with normal polyribosomes for the capacity to support polypeptide chain synthesis in cell-free conditions. The following observations are made: a) no difference is found for the profile on sucrose density gradients; b) partially inactive polyribosomes carry growing polypeptide chains in reduced amounts in comparison with active polyribosomes; c) partially inactive polyribosomes are not capable to release "run off" 80 S ribosomal monomers and to dissociate to active ribosomal subunits. These data are interpreted as the evidence for a block of chain termination producing inactivation of polyribosomes during the late maturation of nucleated erythroid cells.

Animals↗
PubMedDate not supplied

Alu sequences are processed 7SL RNA genes.

7SL RNA is an abundant cytoplasmic RNA which functions in protein secretion as a component of the signal recognition particle. Alu sequences are the most abundant family of human and rodent middle repetitive DNA sequences (reviewed in ref. 2). The primary structure of human 7SL RNA consists of an Alu sequence interrupted by a 155-base pair (bp) sequence that is unique to 7SL RNA. In order to obtain information about the evolution of the Alu domain of 7SL RNA, we have determined the nucleotide sequence of a cDNA copy of Xenopus laevis 7SL RNA and of the 7SL RNA gene of Drosophila melanogaster. We find that the Xenopus sequence is 87% homologous with its human counterpart and the Drosophila 7SL RNA is 64% homologous to both the human and amphibian molecules. Despite the evolutionary distance between the species, significant blocks of homology to both the Alu and 7SL-specific portions of mammalian 7SL RNA can be found in the insect sequence. These results clearly demonstrate that the Alu sequence in 7SL RNA appeared in evolution before the mammalian radiation. We suggest that mammalian Alu sequences were derived from 7SL RNA (or DNA) by a deletion of the central 7SL-specific sequence, and are therefore processed 7SL RNA genes.

Animals↗
PubMedDate not supplied

Upstream sequences modulate the internal promoter of the human 7SL RNA gene.

The human genome is rich in sequences which are structurally related to the 7SL RNA component of the signal recognition particle. The 7SL DNA sequence family consists of four 7SL genes, 500 7SL pseudogenes (which are truncated at one or both ends of the 7SL sequence) and 500,000 Alu sequences. Both 7SL genes and Alu elements are transcribed by RNA polymerase III, and we show here that the internal 7SL promoter lies within the Alu-like part of the 7SL gene. Why then does RNA polymerase III transcribe the few 7SL genes so efficiently, while transcripts from the far more abundant Alu elements are not readily detectable? We find that a human 7SL gene and a synthetic Alu sequence derived from it are expressed 50-100-fold more efficiently in vitro than either a representative Alu element or two 7SL pseudogenes. 5' Deletion and insertion mutants of the 7SL gene demonstrate that, in conjunction with the internal promoter, the first 37 nucleotides upstream from the transcription start site are essential for efficient and accurate initiation in vitro. We suggest that the genomic sequences upstream from most Alu elements and 7SL pseudogenes do not contain this element, and consequently that only a small subset of such sequences can be transcribed in vivo. This may help to explain the homogeneity of the Alu family within each mammalian genome, as well as the species-specific differences between mammalian Alu families.

Base Sequence↗
PubMedDate not supplied

Mouse foetal development: translational inactivation of globin genes during the terminal differentiation of yolk sac erythroid cells.

The molecular mechanism of globin genes inactivation has been explored at the translational level in yolk sac erythroid cells from mouse foetuses. Ageing of the messenger molecules is paralleled by a progressive decrease of the poly(A) tail. Poly(A) less messengers are less active when tested in a wheat germ cell free system and become uncapable to terminate globin chain elongation.

Age Factors↗