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C L Jahn

Publications and source records attributed to C L Jahn.

At least 37 records · Page 2Linked to original sources
PubMed1988

Bal31 sensitivity of micronuclear sequences homologous to C4A4/G4T4 repeats in Oxytricha nova.

The sequence similarity and functional equivalence of telomeres from macronuclear linear DNA molecules in Oxytricha and telomeric sequences of true mitotic/meiotic chromosomes suggest that the (C4A4)n/(G4T4)n sequences found at macronuclear telomeres may also function as micronuclear telomeres in Oxytricha. In this study, radioactively labeled (C4A4)n have been hybridized to micronuclear DNA samples that have been treated with the enzyme Bal31, which has double-stranded exonuclease activity. A time course of digestion shows that approximately 50% of the micronuclear sequences that hybridize to a C4A4 probe disappear with mild digestion by Bal31, suggesting that these sequences are telomeric. The remainder of the hybridizing sequences are not degraded any more rapidly than the total genomic DNA. All of the C4A4/G4T4 sequences that can be detected by hybridization of C4A4 probes to Southern-blotted restriction enzyme digests of micronuclear DNA occur in regions of the genome that are highly resistant to restriction enzyme digestion and show a clustering of sites reminiscent of telomeres in other organisms. We propose that the micronuclear C4A4 hybridizable sequences that are Bal31 resistant may be located near the telomere and within telomere-associated repetitive sequences that are immediately internal to telomeric (Bal31 sensitive) C4A4 hybridizeable sequences.

Animals↗
PubMed1988

Organization of the Euplotes crassus micronuclear genome.

Euplotes crassus, like other hypotrichous ciliated protozoa, eliminates most of its micronuclear chromosomal DNA in the process of forming the small linear DNA molecules that comprise the macronuclear genome. By characterizing randomly selected lambda phage clones of E. crassus micronuclear DNA, we have determined the distribution of repetitive and unique sequences and the arrangement of macronuclear genes relative to eliminated DNA. This allows us to compare the E. crassus micronuclear genome organization to that of another distantly related hypotrichous ciliate, Oxytricha nova. The clones from E. crassus segregate into three prevalent classes: those containing primarily eliminated repetitive DNA (Class I); those containing macronuclear genes in addition to repetitive sequences (Class II); and those containing only eliminated unique sequence DNA (Class III). All of the repetitive sequences in these clones belong to the same highly abundant repetitive element family. Our results demonstrate that the sequence organization of the E. crassus and O. nova micronuclear genomes is related in that the macronuclear genes are clustered together in the micronuclear genome and the eliminated unique sequences occur in long stretches that are uninterrupted by repetitive sequences. In both organisms a single repetitive element family comprises the majority of the eliminated interspersed middle repetitive DNA and appears to be preferentially associated with the macronuclear sequence clusters. The similarities in the sequence organization in these two organisms suggest that clustering of macronuclear genes plays a role in the chromosome fragmentation process.

Animals↗
PubMed1984

The complete nucleotide sequence of a beta-globin-like structure, beta h2, from the [Hbb]d mouse BALB/c.

We have determined the complete nucleotide sequence of beta h2, a pseudogene in the mouse beta-globin gene complex. The structure of beta h2 is analogous to that of a normal beta-globin gene, and its nucleotide sequence shares 72% homology with the coding regions of a reference mouse adult beta-globin gene. A frame shift occurs in the first coding region for which a compensatory splicing scheme can be devised. The reading frame is not otherwise disrupted. All of the recognized transcription, translation, and splicing signals in beta h2 are intact, with the exception of the " CCAAT box," which has been altered to GTAAC . We compared the predicted amino acid sequence of beta h2 with other beta-globin sequences. Evidence for a period of divergence without selection in the history of beta h2 was found in a set of codons that are usually highly conserved in productive beta-globin genes. An evolutionary tree constructed from nucleotide sequence suggests that beta h2 originated from the adult genes at least 60 million years ago. After some period as a productive gene, beta h2 was inactivated and has subsequently diverged without selection. Hybridization experiments demonstrated that beta h2 and the surrounding region occur without major alteration in other rodent species. The sequence ( AGCCA - 4n - GTGT ) occurs 5' of the CCAAT box in beta h2 and in many productive globin genes.

Animals↗
PubMed1984

Internal sequences are eliminated from genes during macronuclear development in the ciliated protozoan Oxytricha nova.

During the life cycle of the hypotrichous ciliate Oxytricha nova, a macronucleus containing short, gene-sized DNA molecules is produced from a copy of the chromosomal micronuclear genome. In order to characterize the process of macronuclear development, we have isolated and determined the DNA sequence of a particular macronuclear gene and its micronuclear precursor. The results of this analysis indicate that macronuclear telomeric sequences (5'C4A4(3') repeats) are not present at the ends of the gene in its micronuclear chromosomal location and must be added during development. In addition, the micronuclear copy of the gene contains three short blocks of sequence that must be removed during development, implying the involvement of a nucleic acid-splicing process in generating mature macronuclear genes.

Amino Acid Sequence↗
PubMed1983

The L1Md long interspersed repeat family in the mouse: almost all examples are truncated at one end.

We have characterized a large repetitive element which has been found at seven different locations within the beta globin locus of the BALB/c mouse. This repeat has an unusual structure in that each of the different members has the same end of the element conserved while the other end terminates at a different point in each repeat member. The sequences within the repeats from the beta globin locus have homology with other repetitive families such as the MIF-1, Bam-5, R, and the BamH1 families. These were recently proposed (T. Fanning, (1983) Nucleic Acids Res. 11, 5073-5091) to be part of a structure with the same organization which we found in the globin locus. Probing plaques from a BALB/c genomic library with sequences derived from the repeats in the globin locus shows that virtually all of the repeats from this family are organized in a manner consistent with the proposed structure.

Animals↗
PubMed1983

Organization of gene and non-gene sequences in micronuclear DNA of Oxytricha nova.

In order to study the derivation of the macronuclear genome from the micronuclear genome in Oxytricha nova micronuclear DNA was partially digested with EcoRI, size fractionated, and then cloned in the lambda phage Charon 8. Clones were selected a) at random b) by hybridization with macronuclear DNA or c) by hybridization with clones of macronuclear DNA. One group of these clones contains only unique sequence DNA, and all of these had sequences that were homologous to macronuclear sequences. The number of macronuclear genes with sequences homologous to these micronuclear clones indicates that macronuclear sequences are clustered in the micronuclear genome. Many micronuclear clones contain repetitive DNA sequences and hybridize to numerous EcoRI fragments of total micronuclear DNA, yielding similar but non-identical patterns. Some micronuclear clones containing these repetitive sequences also contained unique sequence DNA that hybridized to a macronuclear sequence. These clones define a major interspersed repetitive sequence family in the micronuclear genome that is eliminated during formation of the macronuclear genome.

Animals↗
PubMed1983

Complete nucleotide sequence of an immunoglobulin VH gene homologue from Caiman, a phylogenetically ancient reptile.

Immunoglobulin variable (V) gene regions typify extensive multigenic families in terms of overall size, chromosomal arrangement and presence of large numbers of apparent pseudogenes. A unique mechanism of somatic reorganization involving recombination of VH, D and JH or VL and JL segments accompanies the differentiation of lymphoid cells and together with somatic mutation and other types of recombination accounts for V-region diversity. Although these processes have been well characterized in higher mammals, little is known concerning their origin and diversification during phylogenetic time. Previously, we described the blot-hybridization characteristics of murine VHIII probes with restriction enzyme-digested genomic DNA isolated from several phylogenetically critical species, including Caiman crocodylus, a modern representative of an ancient reptilian subclass. Here we have used a murine probe, S107V, to select homologous clones from a library of Caiman genomic DNA constructed in a lambda bacteriophage. The complete nucleotide sequence of a Caiman gene homologous to the murine VH gene and its adjacent 5' and 3' region is described. Comparison of the sequence with mammalian prototypes shows evidence of considerable organizational and structural homology extending outside the presumed VH-coding region and including elements believed to be involved in somatic recombination. Inferences about the evolution of this multigenic family can now be extended to the level of phylogenetic class.

Alligators and Crocodiles↗
PubMed1982

Multiple components in restriction enzyme digests of mammalian (insectivore), avian and reptilian genomic DNA hybridize with murine immunoglobulin VH probes.

High molecular weight genomic DNAs isolated from an insectivore, Tupaia, and a representative reptilian, Caiman, and avian, Gallus, were digested with restriction endonucleases transferred to nitrocellulose and hybridized with nick-translated probes of murine VH genes. The derivations of the probes designated S107V (1) and mu 107V (2,3) have been described previously. Under conditions of reduced stringency, multiple hybridizing components were observed with Tupaia and Caiman; only mu mu 107V exhibited significant hybridization with the separated fragments of Gallus DNA. The nick-translated S107V probe was digested with Fnu4H1 and subinserts corresponding to the 5' and 3' regions both detected multiple hybridizing components in Tupaia and Caiman DNA. A 5' probe lacking the leader sequence identified the same components as the intact 5' probe, suggesting that VH coding regions distant as the reptilians may possess multiple genetic components which exhibit significant homology with murine immunoglobulin in VH regions.

Alligators and Crocodiles↗
PubMed1981

Locations of three repetitive sequence families found in BALB/c adult beta-globin clones.

Three different repeat sequences have been mapped within the cloned EcoRI fragments that contain the adult beta-globin genes from the BALB/c (Hddd) mouse. One sequence, "a", occurs 1.5-2 kb 3' to the beta-major gene. A second, "b", is found 4kb 5' and 7.5kb 3' to the beta-minor gene. The 14kb EcoRI fragment bearing the beta-minor gene carries at least one additional repetitive element, "c". Probing a BALB/c DNA library with each repeat has demonstrated that these sequences are moderately to highly repetitive and are extensively interspersed with each other throughout the genome. In addition, repeats "a" and "b" are preferentially found in satellite and main-band DNa, respectively. The occurrence of these repeats elsewhere in the beta-globin cluster was demonstrated by probing the non-adult globin clones with each repeat. The arrangement of these repeats around the non-adult genes is 5'-"b"-"b"-epsilon y-beta hl-beta h2-"c"-beta h3-3'. Probing the C57BL/10 (Hbbs) adult gene clones with these repeats demonstrated that the distribution of these sequences in the adult region of these two haplotypes is essentially the same.

Animals↗
PubMed1981

The adult beta-globin genes of the "single" type mouse C57BL.

A set of four clones containing the two adult beta-globin genes of the "single" type mouse C57BL/10 (genotype Hbbs/Hbbs) were isolated from a library of cloned restriction fragments. The two genes, designated beta s and beta t, were physically mapped onto a 32 kb segment of the chromosome carried by the four clones. Beta s and beta t form a stable heteroduplex 1850 bp long, indicating that they are intact and conserved at this level of resolution throughout their length, including their intervening sequences. The beta s gene allelic with the beta dmaj gene of the BALB/c mouse (genotype Hbbd/Hbbd). These two alleles, as well as their surrounding sequences, are highly conserved. In contrast, heteroduplexes of beta t with its BALB/c allele, beta dmin, revealed three extensive but localized rearrangements. One region of non-homology falls within the large intervening sequence, IVS2. To the 5' side of the beta/beta dmin gene position two unequal substitutions were observed; each results in the net insertion of about 1000 bp into the Hbbd chromosome. The beta/b dmin gene position is bracketed by a 1450 bp inverted repeat. One of the 1000 bp substitutions maps within this inverted repeat.

Animals↗
PubMed1980

DNA sequence organization of the beta-globin complex in the BALB/c mouse.

Clones containing five non-adult beta-globin genes were isolated from a library of BALB/c DNA. Together, the newly cloned regions comprise a contiguous block of 32 kb of the mouse genome. Restriction mapping of genomic DNA established the physical linkage of these non-adult genes to the two adult beta-globin genes as well as the two adult genes to each other. Thus this entire BALB/c beta-globin complex consists of seven linked genes, all with the same transcriptional orientation, arrayed over 70 kb of DNA. The order of these genes is: 5'-epsilon y3-beta h0-beta h1-beta h2-beta h3-beta major-beta minor-3' Portions of each of the five newly identified genes have been sequenced. Only one, epsilon y3, encodes a previously described globin. beta h0 and beta h1, which are closely related, differ significantly from both adult and embryonic globins. The beta h2 sequence is more closely related to the adult genes than to the other non-adult genes. However, it is the sequence least homologous to both of these classes. The 5' half of the beta h3 gene (preceding codon 75) has an aberrant structure. The rest of this sequence is intact, resembling an adult beta-globin gene except for an inserted base at cocon 90, resulting in a frameshift. Consequently, the beta h3 sequence cannot be translated to produce a normal beta-globin.

Animals↗
PubMed1976

Stability of RNA synthesized by the mouse oocyte during its major growth phase.

The RNA of growing mouse oocytes and ovulated ova was labeled by injection of a solution containing tritiated uridine into the ovarian bursa. The time course of incorporation into RNA by oocytes was followed by analysis of alkali-labile acid insoluble radioactivity and by autoradiography. The results show that most of the incorporation into RNA by growing oocytes takes place within one day of bursal injection of the precursor, reflecting the rapid fall of label in the acid soluble precursor pool. The RNA of growing oocytes of all sizes is unusually stable, at least 80% of the labeled RNA present two days after bursal injection being retained until ovulation 10 to 20 days later. The fraction of heterogeneous RNA in labeled RNA of ova was estimated as 20% by sucrose gradient analysis. It is likely that egg RNA is synthesized primarily during the period of oocyte growth one to three weeks before ovulation.

Animals↗