Biomedical subjects

S Mounir

Publications and source records attributed to S Mounir.

25 records · Page 2Linked to original sources

PubMed1992

Sequence analysis of the membrane protein gene of human coronavirus OC43 and evidence for O-glycosylation.

The gene encoding the membrane (M) protein of the OC43 strain of human coronavirus (HCV-OC43) was amplified by a reverse transcription-polymerase chain reaction of viral RNA with HCV-OC43- and bovine coronavirus (BCV)-specific primers. The nucleotide sequence of the cloned 1.5 kb fragment revealed an open reading frame (ORF) of 690 nucleotides which was identified as the M protein gene from its homology to BCV. This ORF encodes a protein of 230 amino acids with an M(r) of 26416. The gene is preceded by the motif UCCAAAC, analogous to the consensus coronavirus transcription initiation sequence. The M protein of HCV-OC43 shows features typical of all coronavirus M proteins studied: a hydrophilic, presumably external N terminus including about 10% of the protein, and a potential N-glycosylation site followed by three major hydrophobic transmembrane domains. The amino acid sequence of the M protein of HCV-OC43 has 94% identity with that of the Mebus strain of BCV, and also contains six potential O-glycosylation sites in the exposed N-terminal domain. Indeed, the glycosylation of the M protein was not inhibited in the presence of tunicamycin, which is indicative of O-glycosylation, as previously reported for BCV and murine hepatitis virus. Virions released from tunicamycin-treated cells contained the M glycoprotein but were devoid of both peplomer (S) and haemagglutinin-esterase (HE) proteins. Thus, inhibition of the N-glycosylation of the S and HE structural proteins prevented their incorporation into progeny virions, an indication that they are dispensable for virion morphogenesis, unlike the M protein.

Amino Acid Sequence↗

PubMed1990

Alternate splice sites within the human VH gene coding sequences lead to truncated Ig mu-chains.

The Burkitt's lymphoma cell lines JBL2 and Ly91 contain intracytoplasmic mu chains without L chain by immunofluorescence. These mu chains and the corresponding cDNA are abnormally short. Detailed analysis of the productive H chain alleles showed that the cell lines JBL2 and Ly91 use a VHIV and a VHIII subgroup gene, respectively. In both cell lines, the 3' part of the V exon was markedly abnormal and contained several stop codons. Point mutations affected the JH6 donor splice site in the JBL2 gene, precluding normal splicing into C mu. Although the JH2 splice site was unmodified in Ly91, it was not used. As in JBL2, splicing occurred at an alternate splice site present 5' of these alterations, thus removing all these abnormalities from the mature transcripts. This alternate splicing explains the presence in both cell lines of truncated mRNA and proteins lacking two-thirds of the V region.

Base Sequence↗

PubMed1990

Immunoglobulin light chain transcripts with altered V regions in Burkitt's lymphoma cell lines producing short mu chains.

The Burkitt lymphoma cell lines Ly91, Ly47 and Ly66 produce short mu chains in the absence of associated light (L) chains. mu mRNA lack two-thirds of the variable (V) region due to an alternate splicing event that takes place within V genes. L chain genes were found to be rearranged in these lines and to lead to transcripts with altered V regions. Although these abnormal transcripts displayed specific abnormalities in each cell line, they shared some features, including large deletions involving the V-J junction. In one cell line, L chain transcripts made up of either V kappa I subgroup gene J kappa 3 or V kappa IV gene-J kappa 4 recombination products bore a similar alteration: the donor splice site of the rearranged J kappa segment was modified, leading to the alternate use of the donor site of either the leader peptide exon or the next 3' unrearranged J kappa segment.

Base Sequence↗

PubMed1990

Production of an abnormal mu chain with a shortened VHIV subgroup variable region in a Burkitt's lymphoma cell line.

The Burkitt's lymphoma cell line Ly66 produces a short mu chain which lacks 4 kDa in apparent molecular mass. Study of the corresponding messenger RNA showed it to be 0.3 kb shorter than normal mu transcripts. The cDNA sequence of the mu transcripts began by a short VH region consisting of the first one-third of a VHIV subgroup gene segment. It was followed by a normal mu constant region. This VH region coded for 38 amino acids, thus differing from two truncated VHIV regions previously reported in other Burkitt's lymphoma cell lines, which were interrupted at codon +26 by an alternate splicing event. In addition, the Ly66 variable sequence bore several point mutations and contained two potential N-glycosylation sites.

Amino Acid Sequence↗

PubMed1988

Burkitt's lymphoma cell lines producing truncated mu immunoglobulin heavy chains lacking part of the variable region.

Burkitt's lymphoma cell lines Ly91, Ly47 and JBL2 contained intracytoplasmic mu chains without light chains and variably expressed membrane mu chains. All three cell lines produced similarly truncated heavy chains with an apparent molecular mass of 64 kDa instead of the normal 74 kDa. Both the intracellular and secreted forms of the mu chains were similarly truncated. The membrane and the secreted forms of mu mRNAs were shorter than normal. The cDNAs contained a leader sequence, followed by about one third of a variable region (VH), then by the constant region (C mu). Interruption of the variable region took place near the end of the framework region 1 (FR 1) in Ly 47 and JBL2, and within the complementarity determining region 1 (CDR1) in Ly91. In the three lines, the joining between VH and C mu maintained the normal open reading frame throughout the variable and constant regions.

Amino Acid Sequence↗

PubMed1985

Distribution of IgG subclass levels in normal adult sera as determined by a competitive enzyme immunoassay using monoclonal antibodies.

IgG subclass levels were measured by an indirect competitive immunoenzymatic assay with selected monoclonal antibodies in sera from 180 adult blood donors. Mean levels were 6.35 mg/ml (65% of the sum of the subclasses) for IgG1, 2.61 mg/ml (26.2%) for IgG2, and 0.414 mg/ml (4.3%) for IgG3. IgG4 levels were significantly different in men (mean 0.456 mg/ml, 4.8% of the sum) and women (mean 0.29 mg/ml, 3.2%), with very wide ranges. The distribution of IgG2 levels was more homogeneous than that of IgG4 but more heterogeneous than those of IgG1 and IgG3, with a number of sera that displayed low levels of IgG2.

Adolescent↗

PubMedDate not supplied

The hepatitis C virus NS5B RNA-dependent RNA polymerase activity and susceptibility to inhibitors is modulated by metal cations.

OBJECTIVES: The aim of this study was to understand the effect of metal cations on the hepatitis C virus (HCV) NS5B in vitro RNA-dependent RNA polymerase (RdRp) activity and its susceptibility to various inhibitors. METHODS: A recombinant full-length HCV NS5B protein was expressed in insect cells and purified to homogeneity. RdRp activity was assessed using standard filtration or polyacrylamide gel-based assays. RESULTS: Efficient inhibition of the HCV NS5B RdRp activity by gliotoxin, as well as by various substrate analogs, occurs in the presence of Mn2+, but not of Mg2+. Assays performed in the presence of both cofactors suggest that, in vitro, the enzyme's affinity for Mn2+ is higher than that for Mg2+. In addition, the RdRp activity, displayed in the presence of heteropolymeric templates, is significantly increased when the metal cofactor consists of Mn2+. Finally, steady state kinetics showed that the velocity of the reaction, as well as the affinity of the enzyme for its substrate, could both be affected by the nature of the divalent metal cation used.

Animals↗