Superfamily expands

Nucleotide sequence analysis of a transforming gene isolated from nasopharyngeal carcinoma cell line CNE2: an aberrant human immunoglobulin kappa light chain which lacks variable region

A transforming gene, designated Tx, was isolated from a human nasopharyngeal carcinoma (NPC) cell line CNE2 by transfection and molecular cloning techniques. The Tx gene was analyzed using computer-based bioinformatics and compared with the known sequences in EMBL and GenBank databases. We found that Tx contains human immunoglobulin kappa light chain constant region, five intact joining regions J1-J5, five recombination signal sequences and an N-segment besides classic regulatory sequences such as TATA boxes, CAAT boxes, poly A signals, etc. Interestingly, Tx also contains several binding sites for nuclear transcription factors such as NF-kappaB, NF-IL6, TFIID, etc. In conclusion, there are only several base pairs mutations or deletions compared with normal Ig K JC gDNA fragment. In all, Tx is an aberrant human immunoglobulin kappa light chain that contains the constant region, five joining regions, which lacks the variable regions.

The limited universe of exons

The catalogue of mosaic proteins showing evidence of exon-shuffling continues to expand. The repeated use of exon modules suggests that current protein diversity could have been generated from a finite set of such exon modules, and that the size and character of this underlying exon universe can still be glimpsed in extant proteins.

The human transmembrane secretory component (poly-Ig receptor): molecular cloning, restriction fragment length polymorphism and chromosomal sublocalization

The human transmembrane secretory component (SC) mediates glandular translocation of polymeric IgA and IgM into exocrine secretions. A 2898-bp cDNA clone, encoding the entire sequence of the human transmembrane SC, was isolated from a colonic adenocarcinoma cell line cDNA library. The deduced amino-acid sequence had a length of 764 residues and showed an overall similarity of 56% and 64% with the rabbit and rat counterpart, respectively. A restriction fragment length polymorphism (RFLP) was found with PvuII, revealing a two-alle RFLP with an autosomal codominant inheritance pattern and allele frequencies of 0.65 and 0.35. Southern blot analysis of human-rodent somatic hybrid panels, including hybrids with translocation chromosomes carrying different parts of chromosome 1, assigned the SC gene to 1q31-q42, thus confirming a previously reported provisional assignment.

Immunogenetic markers as probes for polymorphism, gene regulation and gene transfer in man--the Gm system in perspective

The genetic markers of immunoglobulins (Ig) demonstrable by immunological methods have shown their usefulness as genetic probes. The study of these allotypes originally proved that Ig production is under conventional genetic control and also established that allelic exclusion is valid for the key molecules of the immune response. The codons responsible for the G1m(a) marker and their position in the human genome are precisely known. This knowledge implies that Gm typing may be used as a convenient and reliable means of following the fate of IgG constant gene segments. Anti-Gm's are common in rheumatoid arthritis. They appear early in the disease and may persist throughout life. The stimulus for their appearance has not yet been established. The anti-Gm's in the allegedly autoimmune disease rheumatoid arthritis are commonly and apparently paradoxically specific for Gm gene products of other persons. Another apparent paradox brought to light by Ig allotype research is the occasional appearance of non-nominal allotypes in contradiction to Mendelian laws. It is proposed that a plausible explanation for these two paradoxes is Ig gene transfer between individuals with viral vectors. Reasons for this proposal and some possible consequences of gene transfer in a polymorphic species are delineated. Immunogenetics and DNA technology in combination provide powerful tools to elucidate the fate of genes. A method allowing the assignment of G1m(a+) and G1m(a-) at the gene level by polymerase chain reaction analysis has recently been established and is briefly described.