Biomedical subjects

M L Tykocinski

Publications and source records attributed to M L Tykocinski.

59 records · Page 4Linked to original sources

PubMed1987

Cloning and characterization of cDNAs encoding the complete sequence of decay-accelerating factor of human complement.

cDNAs encoding the complement decay-accelerating factor (DAF) were isolated from HeLa and differentiated HL-60 lambda gt cDNA libraries by screening with a codon preference oligonucleotide corresponding to DAF NH2-terminal amino acids 3-14. The composite cDNA sequence showed a 347-amino acid protein preceded by an NH2-terminal leader peptide sequence. The translated sequence beginning at the DAF NH2 terminus encodes four contiguous approximately equal to 61-amino acid long repetitive units of internal homology. The repetitive regions contain four conserved cysteines, one proline, one glycine, one glycine/alanine, four leucines/isoleucines/valines, one serine, three tyrosines/phenylalanines, and one tryptophan and show striking homology to similar regions previously identified in factor B, C2, C4 binding protein, factor H, C1r, factor XIII, interleukin 2 receptor, and serum beta 2-glycoprotein I. The consensus repeats are attached to a 70-amino acid long segment rich in serine and threonine (potential O-glycosylation sites), which is in turn followed by a stretch of hydrophobic amino acids. RNA blot analysis of HeLa and HL-60 RNA revealed three DAF mRNA species of 3.1, 2.7, and 2.0 kilobases. The results indicate that portions of the DAF gene may have evolved from a DNA element common to the above proteins, that DAF cDNA predicts a COOH-terminal anchoring polypeptide, and that distinct species of DAF message are elaborated in cells.

Amino Acid Sequence↗

PubMed1985

Structure of a functional rabbit class I MHC gene: similarity to human class I genes.

Studies of rabbit major histocompatibility complex proteins have suggested that rabbits express only a single class I antigen, in contrast to most mouse strains (H-2K, D, and L) and man (HLA-A, -B, and -C), which express three. To explore the significance and the molecular basis of this apparent species difference, we have characterized the expressed class I protein and a corresponding cDNA clone from the rabbit cell line RL-5, which is derived from the inbred B/J rabbit strain. As an extension of these analyses, this report documents the genomic sequence of a gene, designated 19-1, which encodes the same histocompatibility antigen expressed in RL-5. The availability of the corresponding full-length cDNA and amino-terminal protein sequence indicates the fully functional nature of the 19-1 gene and allows presumptive assignment of the transcription start site and delineation of exon/intron boundaries. Comparisons of the rabbit gene with homologous human and mouse sequences reveal a striking similarity between 19-1 and human genes in both exon/intron organization and specific nucleotide sequences; this close similarity allows tentative identification of previously unrecognized transcriptional start sites in the human genes.

Animals↗

PubMed1984

CG dinucleotide clusters in MHC genes and in 5' demethylated genes.

In the DNA of higher vertebrates the dinucleotide CG is unique in two respects: it occurs far less frequently than would be expected on the basis of the content of cytosine and guanine in a given DNA segment ("CG suppression") and it contains predominantly 5-methyl-cytosine, the only modified nucleotide common in vertebrate DNA. Here we point out the existence of CG clusters, i.e. localized lapses in the usual CG suppression, in two categories of DNA segments from vertebrates: around the polymorphic exons of major histocompatibility complex (MHC) genes and in the 5' regions of certain other genes. These observations contradict the recent suggestion that CG frequency is uniform over long contiguous segments of DNA containing several genes. A model for the origin of these CG clusters as a consequence of regional demethylation of germline DNA is supported by analysis of other sequence features of these regions as well as by previously published data on the methylation status in sperm DNA of two of these CG-rich regions.

Animals↗

PubMed1984

Rabbit class I MHC genes: cDNA clones define full-length transcripts of an expressed gene and a putative pseudogene.

The rabbit cell line RL-5 was recently found to express only a single detectable major histocompatibility complex class I protein, in contrast to the multiple class I proteins expressed in cells of the mouse (K, D, and L) and human (A, B, and C). To clarify this difference in the rabbit major histocompatibility complex, we have begun an investigation of the class I genes expressed in the RL-5 cell line and here report the construction of 31 class I cDNA clones derived from RL-5 mRNA. Restriction endonuclease mapping has allowed classification of these clones into five groups, apparently representing five distinct class I mRNA transcripts. The sequence of a full-length cDNA from the predominant group (representing 26 of the 31 clones) reveals a typical class I structure, with an amino terminus that exactly matches the 36 amino terminal residues previously determined for the class I protein immunoprecipitated from RL-5. Complete sequence of a second distinct class I mRNA transcript was deduced from cDNA clones of the second largest group (representing two of the 31 clones). Although this transcript corresponds to a complete class I sequence, an anomaly in initiation sequence may preclude its translation in the proper reading frame. Comparison of the rabbit class I sequences to those of mouse and human revealed significantly higher homologies between the rabbit and the human than between mouse and rabbit or mouse and human sequences.

Amino Acid Sequence↗

PubMed1982

Rabbit MHC antigens: occurrence of non-beta-2-microglobulin-associated class I molecules.

Two monoclonal antibodies, L12/36 and L13/112, prepared from spleens of BALB/c mice immunized with extracts of the rabbit lymphoid cell line RL-5, precipitate a 42,000 mol. wt molecule from detergent lysates of this cell line. This molecule is not associated with beta-2-microglobulin (beta 2m) and has been shown by sequential precipitation experiments to be antigenically distinct from the population of class I rabbit MHC (RLA) molecules that is associated with beta 2m. In spite of this antigenic difference, amino acid sequence analyses indicate that the RLA heavy chain precipitated with anti-beta 2m and that precipitated with the monoclonal antibodies, have identical N-terminal sequences. The sequence determined to position 36 is GSHSMRYFYTSVSRPGLGXPRFIIVGYVXXTXFVRF. The isoleucine assigned to position 24 is the first species-specific residue found for RLA class I molecules. Analysis of the beta 2m associated and non-associated molecules by two-dimensional gel electrophoresis revealed no differences between the RLA heavy chains. Differences in the subcellular locations of the determinants were indicated by fluorescence microscopy and confirmed by immunoelectron microscopy. It was shown that the specificity recognized by the monoclonal antibodies is principally located on the cytoplasmic face of the plasma membrane whereas the majority of anti-beta 2m reactive specificities are on the extracellular side of the cell membrane.

Amino Acid Sequence↗