Restriction fragment length polymorphism of the human T cell receptor alpha gene

Previous studies have demonstrated restriction fragment length polymorphisms (RFLP) in the vicinity of the alpha and beta genes of the human T-cell receptor. In the course of experiments designed to discover additional polymorphic restriction sites, we found a new RFLP of the T-cell alpha gene recognized by the restriction enzyme Taq I. The site was localized to the interval between the most 3 joining (J) exon and the most 5 constant (C) region exon, about 7 kb distant from the previously described Bgl II polymorphic site which mapped to the vicinity of the 3 untranslated exon. With the use of these two polymorphic markers, four Ti-alpha alleles could be identified, allowing unambiguous assignment of all Ti-alpha genes in some families. These markers may be useful in identifying possible immune response genes or disease predisposition genes associated with the genes of the T-cell receptor for antigen.Abbreviations used in this paper RFLP restriction fragment length polymorphism - Ti-alpha alpha gene of the T-cell receptor for antigen     

Predominant T cell receptor gene elements in TNP-specific cytotoxic T cells.

H-2b class I-restricted, TNP-specific CTL clones were obtained by limiting dilution cloning of either short term polyclonal CTL lines or spleen cells of TNP-immunized mice directly ex vivo. Sequence analyses of mRNA coding for TCR alpha- and beta-chains of 11 clones derived from CTL lines from individual C57BL/6 mice revealed that all of them expressed unique but clearly nonrandom receptor structures. Five alpha-chains (45%) employed V alpha 10 gene elements, and four of those (36%) were associated with J beta 2.6-expressing beta-chains. The alpha-chains from these four TCR, moreover, contained an acidic amino acid in position 93 of their N or J region-determined sequences. Clones isolated directly from spleen cells carried these types of receptors at lower frequency, 27% V alpha 10 and 19% J beta 2.6, indicating that bulk in vitro cultivation on Ag leads to selection for these particular receptors. However, even in TNP-specific CTL cloned directly ex vivo, V alpha 10 usage was increased about fivefold over that in Ag-independently activated T cells in H-2b mice (4 to 5%). The selection for V alpha 10/J beta 2.6-expressing cells was obtained repeatedly in other TNP-specific CTL lines from C57BL/6 mice but not in FITC-specific CTL from the same strain or in TNP-specific CTL lines from B10.BR (H-2k) or B10.D2 (H-2d) mice. We conclude from this (a) that the selection for V alpha 10/J beta 2.6+ T cells is driven by the complementarity of these receptors to a combination of TNP and MHC epitopes and (b) that predominant receptor structures reflect the existence of a surprisingly limited number of "T cell-relevant" hapten determinants on the surface of covalently TNP-modified cells.     

Random length assortment of human and mouse T cell receptor for antigen alpha and beta chain CDR3.

In view of the recently determined three-dimensional structures of complexes formed by the T cell receptor for antigen (TCR), the processed peptide and the MHC class I molecule, it is expected that the combined configuration formed by the third complementarity determining regions (CDR3) of TCR alpha and beta chains will be very restricted in size and shape due to the limited length variations of the processed peptides. Thus, the combined TCR alpha and beta chain CDR3 lengths should have a fairly narrow distribution. This feature can be due to the selective association of long alpha chain CDR3 with short beta chain CDR3 and vice versa or due to random assortment of alpha and beta chain CDR3 of even narrower length distribution. Based on existing translated amino acid sequence data, it has been found that the latter mechanism is responsible.     

Smad-dependent cooperative regulation of interleukin 2 receptor alpha chain gene expression by T cell receptor and transforming growth factor-beta

The interleukin 2 receptor alpha chain (IL-2Ralpha) is a component of high affinity IL-2 receptors and thus critically regulates T cell growth and other lymphoid functions. Five positive regulatory regions together control lineage-restricted and activation-dependent IL-2Ralpha induction in response to antigen and IL-2. We now show that TGF-beta cooperates with T cell receptor (TCR) signaling to increase IL-2Ralpha gene expression. Moreover, we identify a sixth positive regulatory region that regulates IL-2Ralpha expression in cells treated with anti-CD3 + anti-CD28 as well as TGF-beta and show that this region contains binding sites for Smad3, AP-1, and cAMP-responsive element-binding protein/ATF proteins. The importance of Smad complexes is indicated by impaired IL-2Ralpha induction by TGF-beta in CD4+ T cells from both Smad3-/- and Smad4-/- mice. Thus, we have identified a novel positive regulatory region in the IL-2Ralpha gene that mediates TGF-beta-dependent induction of the gene. These findings have implications related to IL-2Ralpha expression on activated T cells and regulatory T cells.     

Association of the human CD3-zeta chain with the alpha beta-T cell receptor/CD3 complex. Clues from a T cell variant with a mutated T cell receptor-alpha chain

The TCR for Ag, on the majority of human T cells, is a disulfide-linked heterodimer composed of TCR-alpha and -beta chains noncovalently associated with the monomorphic CD3 complex composed of the CD3-gamma, -delta, -epsilon, and -zeta chains. The interactions involved in the assembly of the various components of this multimeric protein complex are not fully understood. In this report, a variant of the human leukemic T cell line Jurkat that synthesized all of the known components of the TCR/CD3 complex but fails to express the TCR/CD3 complex at the cell surface is further characterized. This variant, J79, has a mutated TCR-alpha chain that does not affect the assembly of the pentameric form (TCR-alpha beta-CD3-gamma delta epsilon) of the TCR/CD3 complex but inhibits the assembly of the CD3-zeta homodimer with the rest of the complex (TCR-alpha beta-CD3-gamma delta epsilon----TCR-alpha beta-CD3-gamma delta epsilon zeta 2). Transfecting a wild-type TCR-alpha gene into J79 reconstituted expression of a complete functionally competent TCR/CD3 complex at the cell surface. The results indicate that the TCR-alpha chain plays a crucial role in the assembly of the CD3-zeta homodimer with the pentameric form of the TCR/CD3 complex.     

合作小型猪T细胞受体α链的基因结构及其多样性

目的探讨猪TCR基因分子结构的复杂性及其与人类的相似性。方法以公开的猪TCRα链基因为参考序列设计两对特异性引物,用RT-PCR法从合作小型猪外周血、淋巴结和脾脏的淋巴细胞中克隆了93个猪TCRα基因(简称STA)。结果测序分析表明,克隆的猪TCRα链的基因均含有可变的信号肽区和V区、高变的J区和恒定的C区的基因片段,但基因间的核苷酸序列组成都不完全相同,且具有十分复杂的多态性和多样性,基因间的同源性在68.4%~98.7%,这与TCRα链的基本基因结构特征相一致。依据TCRα基因的同源性对其分子结构、遗传演化关系和归类分析发现,在其信号肽区、FR1区和CDR1区、FR2区和CDR2区以及FR3区和CDR3区都存在一些变异集中点和变异热点区。用IMGT/V-QUEST分析方法可将合作小型猪TCRαV区(STAV)、J区(STAJ)基因片段与人类的进行比较分析,发现合作小型猪TCRα与人类的遗传演化关系较近,每个序列都能找到与人类对应的TRAV、TRAJ基因片段,甚至V区的相似性可达92%以上。结论近交培育的合作小型猪在正常状态具有应对外界复杂微生物等环境的TCR遗传多样性分子基础,且适合作为人类免疫学及疾病研究的动物模型。     

Promoter and enhancer elements from the rat elastase I gene function independently of each other and of heterologous enhancers.

An elastase-human growth hormone (hGH) fusion gene containing 205 base pairs of elastase 5' flanking region is expressed exclusively in pancreatic acinar cells of transgenic mice. This paper shows that the promoter region (-72 to +8) and the enhancer (-205 to -73) function independently of each other. The elastase enhancer can activate the heterologous mouse metallothionein gene and the hGH gene promoters; conversely, enhancers from the thymocyte-specific murine leukemia virus MCF13 and the metal regulatory elements from the metallothionein gene can activate the elastase promoter in a variety of cell types. Combinations of immunoglobulin and elastase enhancers with a heterologous promoter and the hGH gene result in expression in all of the tissues predicted by the sum of each enhancer acting alone. Thus these enhancer elements act independently of each other, suggesting that they do not have silencing activity in cells in which they are normally inactive.     

Amplified, overexpressed and rearranged epidermal growth factor receptor gene in a human astrocytoma cell line

We report here that SK-MG-3, a human astrocytoma cell line with a high number of epidermal growth factor (EGF) receptors, has an amplified and overexpressed EGF receptor gene. Northern blot analysis did not show any abnormal EGF receptor gene-related mRNA species. No amplification or rearrangement was noted in 21 other astrocytoma cell lines. In contrast to other cell lines that have EGF receptor gene amplifications, we have not detected inhibition of in vitro proliferation of the SK-MG-3 line by EGF.