PubMed Health⌕ Search

Biomedical subjects

A Annweiler

Publications and source records attributed to A Annweiler.

5 recordsLinked to original sources
PubMed1992

Functional analysis of defined mutations in the immunoglobulin heavy-chain enhancer in transgenic mice.

We have analyzed the effect of defined mutations in the mouse immunoglobulin heavy-chain enhancer after introduction into the germline of transgenic mice. We have tested a mutation of the enhancer octamer motif, a double mutation of the octamer motif and the microB-site, and a triple mutation in the microE2, microE3 and microE4-sites. All constructs are expressed in the spleen of transgenic mice. Furthermore, expression is exclusively detectable in lymphoid organs and not in several nonlymphoid tissues. Whereas mutations in the microE-sites have a more pronounced effect on transgene activity in thymocytes as compared to bone marrow and spleen cells, the octamer/microB double mutation shows significantly reduced expression levels only in B-cells. Finally, our results demonstrate that the intronic heavy-chain enhancer element does not contribute to the increase steady state levels of heavy-chain mRNA after stimulation of spleen cells with LPS.

Animals↗
PubMed1992

Oct2 transactivation from a remote enhancer position requires a B-cell-restricted activity.

Previous cotransfection experiments had demonstrated that ectopic expression of the lymphocyte-specific transcription factor Oct2 could efficiently activate a promoter containing an octamer motif. Oct2 expression was unable to stimulate a multimerized octamer enhancer element in HeLa cells, however. We have tested a variety of Oct2 isoforms generated by alternative splicing for the capability to activate an octamer enhancer in nonlymphoid cells and a B-cell line. Our analyses show that several Oct2 isoforms can stimulate from a remote position but that this stimulation is restricted to B cells. This result indicates the involvement of either a B-cell-specific cofactor or a specific modification of a cofactor or the Oct2 protein in Oct2-mediated enhancer activation. Mutational analyses indicate that the carboxy-terminal domain of Oct2 is critical for enhancer activation. Moreover, this domain conferred enhancing activity when fused to the Oct1 protein, which by itself was unable to stimulate from a remote position. The glutamine-rich activation domain present in the amino-terminal portion of Oct2 and the POU domain contribute only marginally to the transactivation function from a distal position.

Animals↗
PubMed1991

Multiple Oct2 isoforms are generated by alternative splicing.

The interaction of the Oct2 transcription factor with the cognate octamer motif ATGCAAAT is a critical determinant of the lymphoid-specific expression of immunoglobulin genes. Ectopic expression of cloned Oct2 cDNA was shown to be sufficient to reconstitute at least some aspects of this regulation in non-lymphoid cells. We describe the isolation and characterization of multiple cDNAs encoding mouse Oct2 from a mature B-cell line and we show that a variety of isoforms of this transcription factor is generated from a single gene by an alternative splicing mechanism. All the isoforms retain the previously characterized POU-domain and are therefore able to bind to the octamer motif. Different amounts of the various isoforms are present within the same B-cell regardless of the developmental stage of B-cell differentiation and at least some of the isoforms are conserved between mouse and humans. In cotransfection experiments we show that all the isoforms are able to activate an octamer containing promoter element in fibroblasts revealing an unexpected functional redundancy. Finally, we show that one of the isoforms encodes the previously described lymphoid-specific Oct2B protein which has been suggested to be involved in the function of the octamer motif in the context of the immunoglobulin heavy-chain (IgH) enhancer.

Amino Acid Sequence↗
PubMed1990

[A low-cost localization technique for high-dose-rate afterloading applicators].

For radiation safety control radiotherapy today needs a method to check the correct position of a HDR-gynecological applicator before afterloading treatment. At the university clinic in Essen, West Germany, a surgical c-X-ray plant was used for the construction of an orthogonal X-ray-photograph plant, which combines illumination and photographs as localisation technique.

Brachytherapy↗