Analysis for linkage between F13A and three chromosome 6 marker loci: evidence for 6pter: F13A:HLA:GL01:cen gene order

Summary The results of the present study provide independent support for F13A:HLA linkage and refine the F13A: HLA and F13A: GLO1 linkage relationships. Analysis of the corresponding recombination fractions for the total paternal F13A:HLA and F13A:GLO1 peak lod scores() indicates a locus order of 6pter: F13A:HLA:GLO1:cen. Lod scores between F13A and PLG, a locus recently assigned to chromosome 6, exclude close linkage between these loci.     

Genomic organization and nucleotide sequences of two corn histone H4 genes

The sea urchin histone H4 gene has been used as a probe to clone two corn histone H4 genes from a lambda gtWES X lambda B corn genomic library. The nucleotide (nt) sequences of both genes showed that the encoded amino acid sequences were identical to that of the H4 of pea and one variant of wheat. The nt sequences of the coding regions showed 92% homology. 5'- and 3'-flanking regions do not show extensive nt sequence analogies. Southern blotting of the EcoRI digested genomic DNA suggests the existence of multiple H4 genes dispersed throughout the genome.     

Independent immunodominant and immunorecessive tumor-specific antigens on a malignant tumor: antigenic dissection with cytolytic T cell clones

We have analyzed the complexity of a unique tumor-specific transplantation antigen expressed by the murine ultraviolet light-induced fibrosarcoma 1591-RE. This tumor is highly immunogenic and is regularly rejected by normal mice. We have derived a cloned cytolytic T cell line showing a reactivity pattern representative of the cytolytic response of the host rejecting this regressor tumor. Using this T cell line (anti-A), variants of 1591-RE (1591-A-) were selected in vitro that had lost the same antigen as progressor variants of 1591-RE selected by the host in vivo. The in vitro derived variant was then used to generate a second T cell clone (anti-B) that recognized an antigen on the parental tumor that had been retained by the variants derived in vitro. Host-selected progressor variants were also found to have retained this antigen. By selecting for variants in vitro from the parental tumor with the anti-B T cell line, it was shown that the two different antigens (A and B) present on the parental tumor were lost independently of each other. Despite the independence of these two antigens, the host T cell response to the parental regressor tumor was invariably restricted to only the "immunodominant" A antigen.     

Further progress towards a catalogue of all Arabidopsis genes: analysis of a set of 5000 non-redundant ESTs

Nearly 7000 Arabidopsis thaliana -expressed sequence tags (ESTs) from 10 cDNA libraries have been sequenced, of which almost 5000 non-redundant tags have been submitted to the EMBL data bank. The quality of the cDNA libraries used is analysed. Similarity searches in international protein data banks have allowed the detection of significant similarities to a wide range of proteins from many organisms. Alignment with ESTs from the rice systematic sequencing project has allowed the detection of amino acid motifs which are conserved between the two organisms, thus identifying tags to genes encoding highly conserved proteins. These genes are candidates for a common framework in genome mapping projects in different plants.     

Comparison of tRNA nucleotidyltransferase from Escherichia coli and Lactobacillus acidophilus.

Purification of tRNa nucleotidyltransferase from Lactobacillus acidophilus ATCC 4963 and Escherichia coli MRE 600 by preparative polyacrylamide gel electrophoresis is described. Both enzymes gave a single band on analytical polyacrylamide-gel electroesis and sodium dodecylsulfate gels. Chromatography of the high speed supernatant from Lactobacillus at low salt concentrations gave three enzyme fractions of molecular weights about 45 000, 90 000, and 120 000. At 1M NaCl only the first enzyme fraction was found. Kinetic data for both enzymes are given.     

Some properties of tobacco protoplast chromatin.

Chromatin was prepared from tobacco-leaf protoplasts. Its solubility in increasing molarities of NaCl was studied and the structure of the soluble fraction observed by electron microscopy. We demonstrate that in plants, the DNA and histones are associated in beaded structures similar to those called omicron-bodies or nucleosomes in animal chromatin. The nucleosomes were associated with DNA in either compact or extended forms. The compact arrangement was predominant in the fraction solubilized between 0.1 and 0.4 M NaCl. The extended form, present at 0.5 and 0.6 M NaCl. showed DNA filaments of various lengths interspacing the nucleosomes. At these ionic strengths ring structures were present, associated with the DNA. At 0.7 M NaCl and above, only DNA filaments were present, occasionally associated with big rings, and nucleosomes were compoetely dissociated. Free DNA molecules were present at all ionic strengths used. The possible origin and significance of the rings are discussed.     

UV-C response of the ribonucleotide reductase large subunit involves both E2F-mediated gene transcriptional regulation and protein subcellular relocalization in tobacco cells

E2F factors are implicated in various cellular processes including specific gene induction at the G1/S transition of the cell cycle. We present in this study a novel regulatory aspect for the tobacco large subunit of ribonucleotide reductase (R1a) and its encoding gene (RNR1a) in the UV-C response. By structural analyses, two E2F sites were identified on the promoter of this gene. Functional analysis showed that, in addition to their role in the specific G1/S induction of the RNR1a gene, both E2F sites were important for regulating specific RNR1a gene expression in response to UV-C irradiation in non-synchronized and synchronized cells. Concomitantly, western blot and cellular analyses showed an increase of a 60 kDa E2F factor and a transient translocation of a GFP-R1a protein fusion from cytoplasm to nucleus in response to UV irradiation.     

Arginine/serine repeats are sufficient to constitute a splicing activation domain

SR proteins are essential pre-mRNA splicing factors that have been shown to bind a number of exonic splicing enhancers where they function to stimulate the splicing of adjacent introns. Members of the SR protein family contain one or two N-terminal RNA binding domains, as well as a C-terminal arginine–serine (RS) rich domain. The RS domains mediate protein–protein interactions with other RS domain containing proteins and are essential for many, but not all, SR protein functions. Hybrid proteins containing an RS domain fused to the bacteriophage MS2 coat protein are sufficient to activate enhancer-dependent splicing in HeLa cell nuclear extract when bound to the pre-mRNA. Here we report progress towards determining the protein sequence requirements for RS domain function. We show that the RS domains from non-SR proteins can also function as splicing activation domains when tethered to the pre-mRNA. Truncation experiments with the RS domain of the human SR protein 9G8 identified a 29 amino acid segment, containing 26 arginine or serine residues, that is sufficient to activate splicing when fused to MS2. We also show that synthetic domains composed solely of RS dipeptides are capable of activating splicing, although their potency is proportional to their size.