The sequence GGCmCGG is resistant to MspI cleavage.

MspI essentially fails to cut the sequence GGCmCGG at enzyme concentrations which give total digestion of CCGG, CmCGG and GGCCGG sites. This result explains why certain sites in mammalian DNA are resistant to both MspI and HpaII and shows that this results from an idiosynchracy of MspI rather than a novel form of DNA methylation at this site in mammalian cells.     

The complete nucleotide sequence of the I-E alpha d immune response gene.

We have isolated and sequenced the complete murine I-E alpha immune response gene of the H-2db haplotype. The I-E alpha d gene consists of 5300 basepairs and is organized into five or possibly six exons that correspond to different domains of the alpha chain. The amino acid sequence deduced from the I-E alpha gene shows 75% homology to its human counterpart, the HLA-DR alpha chain. The absence of I-E antigen in H-2 mice is due to lack of E alpha chain synthesis. We show here that this defect is caused by a deletion in the 5' end of the I-E alpha b gene.     

TheTy1-copia group retrotransposons inVicia species: copy number,sequence heterogeneity and chromosomal localisation

We present an in-depth study of theTy1-copia group of retrotransposons within the plant genusVicia, which contains species with widely differing genome sizes. We have compared the numbers and sequence heterogeneities of these genetic elements in three diploidVicia species chosen to represent large (V. faba, 1C=13.3 pg), medium (V. melanops, 1C=11.5 pg) and small (V. sativa, 1C=2.3 pg) genomes within the genus. The copy numbers of the retrotransposons are all high but vary greatly, withV. faba containing approximately 10⁶ copies,V. melanops about 1000 copies andV. sativa 5000 copies. The degree of sequence heterogeneity ofTy1-copia group elements correlates with their copy number within each genome, but neither heterogeneity nor copy number are related to the genome size of the host. In situ hybridization to metaphase chromosomes shows that the retrotransposons inV. faba are distributed throughout all chromosomes but are much less abundant in certain heterochromatic regions. These results are discussed in the context of plant retrotransposon evolution.     

Sequence analysis of WIS-2-1A,a retrotransposon-like element from wheat

WIS-2-1A, a 8624 bp insertion in the Glu-1A-2 locus of chromosome 1A of wheat, consists of two 1755 bp long terminal repeats enclosing a 5114 bp internal region. No long open reading frames could be found, but inspection of the predicted amino acid sequence showed regions with homology to retrotransposon structures, including a methionine tRNA initiator binding site, a nucleotide binding domain, a protease, an integrase and a polymerase. DNA replication errors have resulted in frame-shifts in the protein coding region, suggesting that retrotransposition of WIS-2-1A, if it occurs, must be mediated by trans-acting factors.