DNA transposition – a major contributor to plant chromosome structure

Higher plant nuclear genomes contain many families of dispersed repeats that change during evolution. Recent evidence from studies on genetically defined transposable elements raises the possibility that many of the dispersed repeats are remnants of such elements. Transposition of DNA has also occurred between mitochondria, chloroplasts and nuclei, a fact that underlines the major role played by DNA transposition in determining the structure of plant genomes.     

Transgenic mice selectively lacking MHC class II (I-E) antigen expression on B cells: an in vivo approach to investigate Ia gene function

The E alpha MHC class II gene with 1.4 kb of 5'-flanking and 0.5 kb of 3'-flanking sequences was introduced into (H-2b X s)F2 mice, which do not express their endogenous E alpha gene. The transgene was expressed in thymic tissue and in adherent spleen cells and was induced in peritoneal exudate cells by gamma-interferon. In contrast to the normal E alpha gene, there was no expression in B lymphocytes. Since transgenic animals made with constructs containing 3.2 kb and 2 kb of 5'-flanking sequences show normal expression pattern of the E alpha gene, it appears that deletion of 5'-flanking sequences between -1.4 kb and -2 kb inactivated or eliminated regulatory sequences required for expression of E alpha specifically in B cells. The presence of pBR327 DNA linked to the -1.4 kb E alpha transgene suppresses expression in peripheral adherent cells, yielding mice expressing E alpha only in the thymus. These mice appear to be tolerant to I-E, as measured in mixed leukocyte response experiments.     

Conformational differences between two wheat (Triticum aestivum) ''high-molecular-weight'' glutenin subunits are due to a short region containing six amino acid differences.

'High-molecular-weight' (HMW, high-Mr) glutenin subunits are protein constituents of wheat (Triticum aestivum) seeds and are responsible in part for the viscoelasticity of the dough used to make bread. Two subunits, numbered 10 and 12, are the products of allelic genes. Their amino acid sequences have been derived from the nucleic acid sequences of the respective genes. Subunit 10 has fewer amino acids than subunit 12, but migrates more slowly on SDS/PAGE (polyacrylamide-gel electrophoresis). This anomaly is due to between one and six of the amino acid differences between the subunits, localized towards the C-terminal end of the proteins. This has been established by making chimaeric genes between the genes for subunits 10 and 12, transcribing and translating them in vitro and analysing the products by SDS/PAGE. The postulated conformational differences between subunits 10 and 12 are discussed in relation to current hypotheses for the structure of HMW glutenin subunits.     

Sequence and structure of the mouse gene coding for the largest neurofilament subunit

We have determined the complete nucleotide sequence of the mouse gene encoding the neurofilament NF-H protein. The C-terminal domain of NF-H is very rich in charged amino acids (aa) and contains a 3-aa sequence, Lys-Ser-Pro, that is repeated 51 times within a stretch of 368 aa. The location of this serine-rich repeat in the phosphorylated domain of NF-H indicates that it represents the major protein kinase recognition site. The nfh gene shares two common intron positions with the nfl and nfm genes, but has an additional intron that occurs at a location equivalent to one of the introns in non-neuronal intermediate filament-coding genes. This additional nfh intron may have been acquired via duplication of a primordial intermediate filament gene.     

Qa-2 antigen encoded by Q7b is biochemically indistinguishable from Qa-2 expressed on the surface of C57BL/10 mouse spleen cells

Qa-2 was immunoprecipitated from the surface of 125I-labeled C57BL/10 (B10) mouse spleen cells and compared with Qa-2 immunoprecipitated from the surface of R1.1 thymoma cells transfected with Q7b. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that Qa-2 glycoproteins from both of these sources have a relative molecular mass of approximately 37 kDa. After treatment with endoglycosidase F, the Qa-2 polypeptide chains derived from C57BL/10 spleen and Q7b-transfected R1.1 cells displayed identical mobilities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis because of removal of N-linked oligosaccharide residues. Furthermore, treatment of Qa-2 proteins from both sources with cyanogen bromide or alpha-chymotrypsin resulted in identical peptide fragmentation patterns. These results therefore provide a biochemical correlation between a cloned Qa-region gene produce expressed on the surface of transfected cells, and the Qa-2 glycoprotein on spleen cells that was described a decade ago by serologic methods.     

The structure and evolution of the spider monkey delta-globin gene

We have isolated the delta-globin gene of the New-World spider monkey, Ateles geoffroyi, and compared its nucleotide sequence with those of other primate delta- and beta-globin genes. Among primate delta-globin genes, the rate of nonsynonymous substitutions is much less than the rate of synonymous substitutions. This suggests that primate delta- globin genes may remain under evolutionary conservation, perhaps because hemoglobin A2 has an as yet unknown physiological importance.