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Biomedical subjects

J R Wells

Publications and source records attributed to J R Wells.

At least 73 records · Page 4Linked to original sources
PubMed1983

H2A.F: an extremely variant histone H2A sequence expressed in the chicken embryo.

A cDNA clone bank has been constructed from chicken embryonic RNA. Clones hybridizing poorly to embryonic histone gene probes were selected as possible variant gene transcripts. The DNA sequence of one cDNA predicts an extremely variant H2A protein (H2A.F), which is 40% divergent from the most abundant H2A protein in chicken erythrocyte chromatin. The H2A.F gene is not highly conserved across large species barriers, but in the chicken there may be a family of linked genes. The H2A.F mRNA is approximately equal to 820 base pairs in length and, unlike most other histone mRNAs, is polyadenylylated. Significantly, the H2A.F transcript shows a limited tissue distribution in the chicken embryo.

Amino Acid Sequence↗
PubMed1982

Independently evolving chicken histone H2B genes: identification of a ubiquitous H2B-specific 5' element.

The DNA sequence of two chicken histone H2B genes has been determined. Both genes code for the same H2B subtype. Except for conserved "promoter" elements, the sequences 5' to the protein coding regions are completely divergent, indicating that the genes are distantly related and are not evolving in concert. This presents an ideal situation for sequence comparisons. We have discovered a 13 bp, H2B specific homology block, 5' CTCATTTGCATAC 3' located close to the "TATA box". This motif is conserved in all H2B gene leader regions so far sequenced. One of the H2B genes is closely linked, in a divergent arrangement, to an H2A gene, and sequence data suggests that the linked genes share promoter elements.

Amino Acid Sequence↗
PubMed1982

Chicken histone H5: selection of a cDNA recombinant using an extended synthetic primer.

We describe the use of a synthetic primer to select a cDNA recombinant clone containing H5 coding sequences. The strategy used was as follows: 1. Prepare oligo(dT) cellulose-bound mRNA from chicken reticulocytes and select 11S-18S material from sucrose gradients. 2. Use this RNA fraction both to prepare a cDNA library and as a template for H5-specific cDNA synthesis using a synthetic primer. 3. Screen out most globin cDNA recombinants with oligo(dT)-primed globin cDNA. 4. Search for H5 recombinants using H5 specific cDNA and verify the identity by DNA sequencing. Our screening suggests an H5 mRNA abundance of about two parts per thousand in chicken reticulocyte poly(A)-containing RNA. The isolation of an H5 cDNA recombinant clone is an initial step in the study of H5 genes and their relationship to H1 and core histone genes.

Amino Acid Sequence↗
PubMed1982

Cryopreservation of the human multipotent stem cell.

Light density human bone marrow cells were cryopreserved, then thawed and tested for their ability to form myeloid (CFUGM), erythroid (BFUE) and mixed myeloid-erythroid colonies in vitro. Proliferation of mixed hematopoietic colonies was supported by conditioned media from a human T-lymphocyte cell line and erythropoietin. All mixed colonies contained neutrophil and erythroid precursors and approximately 25% had mononuclear phagocytes. Following cryopreservation the bone marrow retained its capacity to form mixed colonies without apparent loss. The recovery of CFUGM and BFUE was 76% and 72% respectively.

Bone Marrow↗
PubMed1981

Vertebrate histone genes: nucleotide sequence of a chicken H2A gene and regulatory flanking sequences.

The DNA sequence of a chicken genomal fragment containing a histone H2A gene has been determined. It contains extensive 5' and 3' flanking regions and encodes a protein identical in sequence to the histone H2A protein isolated from chicken erythrocytes. In the 5' flanking region, a possible "TATA box" and three possible "cap sites" can be recognised upstream from the initiation codon. To the 5' side of the "TATA box" is found an unusual sequence of 21 A's interrupted by a central G residue. It occupies the same relative position as the P. miliaris H2A gene-specific 5' dyad symmetry sequence and the "CCAAT box" seen in other eukaryotic polymerase II genes but is clearly different from both. A significant feature of the 3' non-coding region is the presence of a 23 base-pair sequence that is nearly identical to a conserved region found in sea urchin histone genes. The coding region is extremely GC rich, with strong selection for these bases in the third position of codons. Not a single coding triplet ends in U. No intervening sequences were found in this gene.

Animals↗
PubMed1981

Isolation of a clone containing human histone genes.

A recombinant clone containing human histone genes has been isolated. The clone, lambda HH-01, was selected from a genomal library using chicken histone cDNA and a cloned fragment containing chicken histone genes as probes. Sub-clones from lambda HH-01 have been mapped and coding regions located with cDNA. The human H3 gene has been identified by DNA sequence analysis.

Amino Acid Sequence↗
PubMed1981

Vertebrate histone gene transcription occurs from both DNA strands.

Three clones containing vertebrate histone genes, two from chicken and one from human have been investigated. DNA from each recombinant within lambda Charon 4A has been strand-separated on agarose gels in the presence of poly r(UG). Southern transfer analysis with histone cDNA indicates that in each case transcription occurs from both strands. These results argue against the possibility of polycistronic transcription of these vertebrate histone genes.

Animals↗
PubMed1981

Effect of cryopreservation on recovery of cells forming colonies in diffusion chambers in mice (CFUD).

The effect of cryopreservation on human and murine hematopoietic precursor cell survival was assessed. A large proportion of CFUC and CFUS was recovered following freezing and thawing. At the same time there was a substantial decrease in the number of cells which form myeloid (CFUDG) and megakaryocytic (CFUDM) colonies in diffusion chambers in mice. We suggest that the CFUDG and CFUDM number should be determined in the autologous bone marrow transplantation setting.

Animals↗
PubMed1979

Isolation of a genomal clone containing chicken histone genes.

We have used enriched chicken histone cDNA to select genomal clones from a chicken library. Because the cDNA probe also contained other sequences, a further screening of positive plagues with negative probes eliminated most non-histone gene clones. One 'positively-selected' genomal clone, lambda CH-01, hybridised with cloned sea-urchin histone genes and also detected histone genes in EcoRI-digested genomal sea-urchin DNA. Limited DNA sequencing of HaeIII fragments identified two sequences within the coding region of chicken histone H2A. A third fragment predicted an amino acid sequence with strong homology to an H1 histone sequence.

Amino Acid Sequence↗
PubMed1979

Molecular cloning and sequence analysis of adult chicken betal globin cDNA.

The molecular cloning and nucleotide sequence analysis of adult chicken beta globin mRNA is reported. DNA sequences derived from in vitro transcrption of globin mRNA were purified and amplified as recombinant DNA using the plasmid pBR322. Sequence analysis of several clones coding for beta globin strongly suggests that transcription errors may be generated near the 5' end of transcripts in vitro by reverse transcription. The complete sequence of the longest beta globin insert containing 51 bases of the 5' untranslated region as well as the complete coding and 3' untranslated regions has been determined.

Amino Acid Sequence↗
PubMed1979

Histone genes are clustered with a 15-kilobase repeat in the chicken genome.

Histone mRNA isolated from 5-day-old chick embryos has been used as a template for complementary DNA (cDNA) synthesis. The resultant cDNA, after removal of sequences complementary to rRNA, was used to detect histone genes in adult chicken genomal DNA. Hybridisation data indicate that the histone genes are repeated about 10-fold in the chicken genome. Restriction endonuclease analysis reveals some sequence heterogeneity in these genes. However, the results show that chicken histone genes are clustered with a basic repeat unit of 15 kilobases.

Alleles↗
PubMed1979

Autotransplantation after in vitro immunotherapy of lymphoblastic leukemia.

We have used in vitro immunotherapy before autologous bone marrow transplantation for three patients with acute lymphoblastic leukemia (ALL). Bone marrow was removed during remission, and mononuclear cells were separated by density-step centrifugation on Ficoll-Hypaque. The cells from each patient were treated with a heteroantiserum and complement to eliminate leukemic cells and were cryopreserved. Following chemotherapy and total body irradiation, the treated marrows were thawed and infused. All the patients showed positive evidence of returning marrow function before death. One patient who survived 4 months showed no evidence of leukemia at post mortem, and marrow sections demonstrated active hematopoiesis of all cell lines.

Bone Marrow Transplantation↗