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U Suter

Publications and source records attributed to U Suter.

97 records · Page 6Linked to original sources
PubMed1989

Expression of human lymphocyte IgE receptor (Fc epsilon RII/CD23). Identification of the Fc epsilon RIIa promoter and its functional analysis in B lymphocytes.

Two species, Fc epsilon RIIa and Fc epsilon RIIb, of the human low-affinity receptor for IgE (Fc epsilon RII/CD23) have recently been described. They differ by only six amino acids in the cytoplasmic N-terminus and are generated by different cell-specific transcriptional start sites that lead to distinct 5'-leader sequences in the corresponding mRNA. In this study, we present the analysis of the promoter which is regulating the expression of the B cell-specific Fc epsilon RIIa. Our data show that this promoter is flanked by several long repetitive elements that are influencing transcription in the Burkitt lymphoma B cell line Jijoye. Serial deletions of the 5'-flanking region of the promoter revealed two major regulatory segments that have either inhibitory or enhancing effects on transcription. In addition, IL-4 caused a two- to four-fold up-regulation of the Fc epsilon RIIa promoter activity and the DNA element responsible was mapped within the first 250 bp of the 5'-flanking region. These results were confirmed by transferring the DNA segment containing the putative IL-4 responsive element to a heterologous thymidine kinase promoter. It was concluded that IL-4 augments the Fc epsilon RIIa expression by transcriptional regulation.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Human Fc epsilon R II and IgE-binding factors.

The low-affinity receptor for IgE (Fc epsilon R II) is mainly expressed on B lymphocytes, although it may also be found on some monocytes, eosinophils, and platelets. The presence of Fc epsilon R II on T cells is still controversial, but our results demonstrate that it is expressed on some HTLV-I-transformed T lymphocytes, and they strongly suggest that it may be found on a small proportion of normal T cells. Fc epsilon R II is a 45-KD glycoprotein containing one N-linked carbohydrate of complex type, O-linked carbohydrates, and sialic acid residues. Fc II is cleaved into soluble fragments with molecular weights of 37, 33, 25, and 12 KD, the first three retain the ability of binding to IgE, i.e., they are IgE-binding factors (IgE-BFs). The enzymes involved in their proteolytic cleavage are cell bound. The cDNA coding for Fc epsilon R II was cloned and functionally expressed. The predicted sequence has no homology with that of murine IgE-BFs which are of T cell origin. However, there is a striking homology with several animal lectins, and since the IgE-binding site is located in the homology region, it is possible that it binds to IgE via the carbohydrates expressed on the Fc region of this immunoglobulin. The expression of Fc epsilon R II on B cells and the release of IgE-BFs are upregulated by interleukin 4 and suppressed by gamma and alpha interferons.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Differentiation, B-Lymphocyte↗
PubMed1987

T-cell-derived IgE-binding factors. II. Purification and characterization of IgE-binding factors produced by human T cell leukemia/lymphoma virus-1-transformed T lymphocytes.

We previously described human T cell leukemia/lymphoma virus-1-transformed T cell clones expressing surface molecules binding to monoclonal antibodies against lymphocyte Fc epsilon receptor (Fc epsilon R) and releasing soluble factors binding to both IgE and to monoclonal antibody to lymphocyte Fc epsilon R. In this study, one such clone (HE1-11) was tested for the presence of mRNA hybridizing with a cDNA probe coding for Fc epsilon R on B cells. Northern blot analysis revealed the presence of the same 1.7 kb Fc epsilon R mRNA in HE1-11 and in RPMI 8866 cells as well as in the macrophage cell line U937, expressing Fc epsilon R. The IgE binding factors (BF) released by HE1-11 cells appeared to be identical to those released by RPMI 8866 cells as shown by 1) one- and two-dimensional sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis and 2) tryptic peptides analysis. IgE-BF are microheterogeneous containing molecules with molecular mass of 25 to 27 kDa and with isoelectric point ranging from 4.5 to 5. Some preparations further contained 16-kDa fragments of IgE-BF. These findings suggest that the gene coding for both Fc epsilon R and IgE-BF may also be expressed on some human T cells.

Antibodies, Monoclonal↗
PubMed1987

Molecular structure of the gene and the 5'-flanking region of the human lymphocyte immunoglobulin E receptor.

Overlapping clones which contain the complete gene encoding the human lymphocyte IgE receptor (MW:45kd; identical with CD23), were isolated from human genomic lambda-libraries. The gene spans approximately 13kb and comprises 11 exons. The 5'-end of the mRNA was mapped by primer extension and S1-mapping, revealing two initiation sites for transcription. Two corresponding TATA boxes were identified by sequencing the 5'-flanking region. A 188bp long inverted repeat was found which flanks the promoter region and could possibly be involved in gene regulation. Exons 9 to 11 code for the IgE-binding domain of the receptor which shows homology to several lectins, particularly to the asialoglycoprotein receptor. A comparison of the exon/intron arrangement of these genes implies that their lectin domains have evolved from a common ancestral cassette.

Base Sequence↗
PubMed1987

Cloning and expression of the cDNA coding for a human lymphocyte IgE receptor.

Low-affinity receptors (Fc epsilon R) and secreted factors (IgE-BF) which bind to immunoglobulins of the IgE isotype play a key role in the regulation of human IgE synthesis. We report here the cloning of a cDNA coding for the Fc epsilon R of the human B-lymphoblast cell line RPMI 8866. The nucleotide sequence of this cDNA predicts a polypeptide with 321 amino acids and a mol. wt of 36,281 daltons. A functional Fc epsilon R capable of binding IgE was expressed in Chinese hamster ovary cells after stable transformation with the cDNA which had been cloned into a mammalian expression vector. Amino acid sequence analysis of IgE-BF purified from RPMI 8866 cells revealed an amino-terminal sequence of 19 residues which coincides with the predicted amino acid sequence of the Fc epsilon R, starting at residues 148 and 150. A computer search with the translated amino acid sequence of the Fc epsilon R revealed a domain of 120 amino acids having striking homology to the human asialoglycoprotein receptors.

Amino Acid Sequence↗