Determinants of Moloney murine leukemia virus Gag-Pol and genomic RNA proportions.

Unlabelled: The Moloney murine leukemia virus (MoMLV) ribonucleoprotein complex is composed of an approximately 20:1 mixture of Gag and Gag-Pol polyproteins plus a single genomic RNA (gRNA) dimer. The mechanisms that regulate these proportions are unknown. Here, we examined whether virion proportions of Gag, Gag-Pol, and gRNA were determined by sampling (that is, if they reflected expression ratios or intracellular concentrations) or more specific recruitment.

Transgenes of the mouse immunoglobulin heavy chain locus, lacking distal elements in the 3' regulatory region, are impaired for class switch recombination.

The immunoglobulin heavy (H) chain class switch is mediated by a deletional recombination event between µ and γ, α, or ε constant region genes. This recombination event is upregulated during immune responses by a regulatory region that lies 3' of the constant region genes. We study switch recombination using a transgene of the entire murine H chain constant region locus.

Oncogenic Myc translocations are independent of chromosomal location and orientation of the immunoglobulin heavy chain locus.

Many tumors are characterized by recurrent translocations between a tissue-specific gene and a proto-oncogene. The juxtaposition of the Ig heavy chain gene and Myc in Burkitt's lymphoma and in murine plasmacytoma is a classic example. Regulatory elements within the heavy chain constant region locus are required for Myc translocation and/or deregulation.

Enhancement of antibody class-switch recombination by the cumulative activity of four separate elements.

Class-switch recombination of Ab isotype is mediated by a recombinational DNA deletion event and must be robustly upregulated during Ag-driven differentiation of B cells. The enhancer region 3' of the Cα gene is important for the upregulation of switch recombination. Using a transgene of the entire H chain C region locus, we demonstrate in this study that it is the four 3' enhancer elements themselves (a total of 4.

Switch recombination and somatic hypermutation are controlled by the heavy chain 3' enhancer region.

Both class switch recombination (CSR) and somatic hypermutation (SHM) require transcription and the trans-acting factor activation-induced cytidine deaminase (AID), and must be up-regulated during antigen-dependent differentiation of B lymphocytes. To test the role of the heavy chain 3' enhancers in both CSR and SHM, we used a BAC transgene of the entire heavy chain constant region locus. Using Cre-loxP recombination to delete a 28-kb region that contains the four known 3' heavy chain enhancers, we isolated lines of BAC transgenic mice with an intact heavy chain locus and paired lines in the same chromosomal insertion site lacking the 3' enhancers.

High ligation of the saphenofemoral junction in endovenous obliteration of varicose veins.

Background: Endovenous radiofrequency (RF) ablation of the greater saphenous vein has become an accepted treatment modality. This study examines if it is necessary to perform high ligation of the saphenous vein to insure success of the procedure.

Study Design: A retrospective chart analysis was conducted on 219 patients who underwent RF ablation for venous insufficiency.

Induced expression of murine gamma2a by CD40 ligation independently of IFN-gamma.

IgG2a, with gamma2a H chains, is important for protection against viruses and other intracellular pathogens. Although a large portion of IgG2a expression is dependent upon IFN-gamma, some germline transcription and switch recombination to the murine gamma2a H chain gene expression are independent of IFN-gamma. We found that agonistic anti-CD40 Abs injected into IFN-gamma-deficient mice induce a > 200-fold increase in the amount of serum Ig2a, while other Ig isotypes are increased by 16-fold or less.

The 3' end of the heavy chain constant region locus enhances germline transcription and switch recombination of the four gamma genes.

The switch in immunoglobulin (Ig) heavy chain class is preceded by germline transcription and then mediated by a DNA recombination event. To study germline transcription and class switch recombination we used transgenic mice with a 230-kilobase bacterial artificial chromosome that included a rearranged VDJ gene and the entire heavy chain constant region locus. In addition to several lines with intact transgenes, we identified two lines in which the heavy chain locus transgene lacked Calpha and everything 3' of it, including the regulatory elements HS3a, HS1-2, HS3b, and HS4.

Receptors and counterreceptors involved in NK-B cell interactions.

In addition to the well-documented effect of NK cells on B cell differentiation via their ability to secrete IFN-gamma, NK cells can also induce, via direct cell-cell interactions, germline transcripts (Igamma2a) necessary for switch recombination to IgG2a. Analysis of the ligand-receptor pairs that could be involved in this induction revealed that the expression of CD48 on B cells is crucial for the induction. NK cells from mice with targeted deletions of either the CD2 or the CD244 gene, both of which encode ligands for CD48, are compromised in their ability to induce B cell Igamma2a expression.

Germline transcription and switch recombination of a transgene containing the entire H chain constant region locus: effect of a mutation in a STAT6 binding site in the gamma 1 promoter.

The switch (S) in H chain class is preceded by germline transcription and then mediated by a DNA recombination event. One of the impediments toward understanding the mechanism is the lack of a system in which a recombinant DNA molecule undergoes cytokine-regulated class S recombination. To study class S recombination, we used transgenic mice with a 230-kb bacterial artificial chromosome that included a rearranged VDJ gene and the entire murine H chain constant region locus.