EMMA--mouse mutant resources for the international scientific community

The laboratory mouse is the premier animal model for studying human disease and thousands of mutants have been identified or produced, most recently through gene-specific mutagenesis approaches. High throughput strategies by the International Knockout Mouse Consortium (IKMC) are producing mutants for all protein coding genes. Generating a knock-out line involves huge monetary and time costs so capture of both the data describing each mutant alongside archiving of the line for distribution to future researchers is critical. The European Mouse Mutant Archive (EMMA) is a leading international network infrastructure for archiving and worldwide provision of mouse mutant strains. It operates in collaboration with the other members of the Federation of International Mouse Resources (FIMRe), EMMA being the European component. Additionally EMMA is one of four repositories involved in the IKMC, and therefore the current figure of 1700 archived lines will rise markedly. The EMMA database gathers and curates extensive data on each line and presents it through a user-friendly website. A BioMart interface allows advanced searching including integrated querying with other resources e.g. Ensembl. Other resources are able to display EMMA data by accessing our Distributed Annotation System server. EMMA database access is publicly available at http://www.emmanet.org.

A single bottleneck in HLA-C assembly

Poor assembly of class I major histocompatibility HLA-C heavy chains results in their intracellular accumulation in two forms: free of and associated with their light chain subunit (beta(2)-microglobulin). Both intermediates are retained in the endoplasmic reticulum by promiscuous and HLA-dedicated chaperones and are poorly associated with peptide antigens. In this study, the eight serologically defined HLA-C alleles and the interlocus recombinant HLA-B46 allele (sharing the HLA-C-specific motif KYRV at residues 66-76 of the alpha1-domain alpha-helix) were compared with a large series of HLA-B and HLA-A alleles. Pulse-labeling experiments with HLA-C transfectants and HLA homozygous cell lines demonstrated that KYRV alleles accumulate as free heavy chains because of both poor assembly and post-assembly instability. Reactivity with antibodies to mapped linear epitopes, co-immunoprecipitation experiments, and molecular dynamics simulation studies additionally showed that the KYRV motif confers association to the HLA-dedicated chaperones TAP and tapasin as well as reduced plasticity and unfolding in the peptide-binding groove. Finally, in vitro assembly experiments in cell extracts of the T2 and 721.220 mutant cell lines demonstrated that HLA-Cw1 retains the ability to form a peptide-receptive interface despite a lack of TAP and functional tapasin, respectively. In the context of the available literature, these results indicate that a single locus-specific biosynthetic bottleneck renders HLA-C peptide-selective (rather than peptide-unreceptive) and a preferential natural killer cell ligand.

Assembly and selective “in synthesis” labeling of quenched fluorogenic protease substrates

Because impaired cellular protease activities are linked to many diseases, such as cancer, inflammation, neurodegeneration, and infection, internally quenched fluorescent peptides have recently been developed as tools for analyzing the specificities of these enzymes. Here we report convenient and cost-effective approaches for the selective "in synthesis" assembly of such substrate peptides for protease assays. Fluorescein and Dabcyl groups were covalently and selectively attached during synthesis to epsilon-amino groups of internal lysines. Functionality was then tested by digestion with leucine aminopeptidase, chymotrypsin, and microsomal vesicles. All peptides proved to be appropriate substrates of the enzymes tested and of the endogenous peptidases in the microsomal vesicles. In summary, we describe an innovative and cheap method to develop completely functional quenched fluorescent peptides that are usable in specific detection of individual proteases, in particular aminopeptidases, in both in vitro and in vivo systems.

Identification of HLA-DRPhebeta47 as the susceptibility marker of hypersensitivity to beryllium in individuals lacking the berylliosis-associated supratypic marker HLA-DPGlubeta69

Background

Susceptibility to beryllium (Be)-hypersensitivity (BH) has been associated with HLA-DP alleles carrying a glutamate at position 69 of the HLA-DP β-chain (HLA-DPGlu69) and with several HLA-DP, -DQ and -DR alleles and polymorphisms. However, no genetic associations have been found between BH affected subjects not carrying the HLA-DPGlu69 susceptibility marker.

Methods

In this report, we re-evaluated an already described patient populations after 7 years of follow-up including new 29 identified BH subjects. An overall population 36 berylliosis patients and 38 Be-sensitization without lung granulomas and 86 Be-exposed controls was analysed to assess the role of the individual HLA-class II polymorphisms associated with BH-susceptibility in HLA-DPGlu69 negative subjects by univariate and multivariate analysis.

Results

As previously observed in this population the HLA-DPGlu69 markers was present in higher frequency in berylliosis patients (31 out of 36, 86%) than in Be-sensitized (21 out of 38, 55%, p = 0.008 vs berylliosis) and 41 out of 86 (48%, p < 0.0001 vs berylliosis, p = 0.55 vs Be-sensitized) Be-exposed controls.

However, 22 subjects presenting BH did not carry the HLA-DPGlu69 marker. We thus evaluated the contribution of all the HLA-DR, -DP and -DQ polymorphisms in determining BH susceptibility in this subgroup of HLA-Glu69 subjects. In HLA-DPGlu69-negatives a significant association with BH was found for the HLA-DQLeu26, for the HLA-DRB1 locus residues Ser13, Tyr26, His32, Asn37, Phe47 and Arg74 and for the HLA-DRB3 locus clusterized residues Arg11, Tyr26, Asp28, Leu38, Ser60 and Arg74. HLA-DRPhe47 (OR 2.956, p < 0.05) resulting independently associated with BH. Further, Be-stimulated T-cell proliferation in the HLA-DPGlu69-negative subjects (all carrying HLA-DRPhe47) was inhibited by the anti-HLA-DR antibody (range 70–92% inhibition) significantly more than by the anti-HLA-DP antibody (range: 6–29%; p < 0.02 compared to anti-HLA-DR) while it was not affected by the anti-HLA-DQ antibody.

Conclusion

We conclude that HLA-DPGlu69 is the primary marker of Be-hypersensitivity and HLA-DRPhe47 is associated with BH in Glu69-negative subjects, likely playing a role in Be-presentation and sensitization.

Responses of peptide-specific T cells to stimulation with polystyrene beads carrying HLA class I molecules loaded with single peptides

Cell-sized microbeads carrying single peptide-loaded HLA class I molecules were prepared for HLA-A2 and HLA-B7 by a simple procedure which transfers single peptide-loaded HLA class I molecules from cultured cells to polystyrene beads using anti-peptide antibodies directed to an intracellular segment of HLA-A alpha chains. The surface density of peptide-loaded HLA class I molecules on beads was comparable to that on the peptide-loaded cells. HLA-A2 beads loaded with an HCV peptide HCV1073 were tested for stimulation activity on an HCV1073-specific CD8+ T cell clone NS3-1. A substantial level of gamma-IFN production was induced. The stimulation was peptide-specific. The efficiency was dependent on the bead concentration and the surface HLA class I density on beads and enhanced significantly by co-coupling of anti-CD28 to peptide-loaded beads. The peptide-loading efficiency on HLA class I molecules and the transfer efficiency of HLA class I molecules to polystyrene beads were reasonably high for HLA-A2 and HLA-B7. Thus, polystyrene beads carrying these single peptide-loaded HLA class I molecules are potentially useful in further analysis of the co-stimulatory or inhibitory factors involved in CD8+ T cell responses and eventually in detection of cytotoxic T cells in PBLs.

Detailed analysis of the effects of Glu/Lys beta69 human leukocyte antigen-DP polymorphism on peptide-binding specificity

The polymorphism at position beta69 of the human leukocyte antigen (HLA)-DP molecule has been associated with susceptibility to several immune disorders and alloreactivity. Using molecular modeling, we have predicted a detailed structure of the HLA-DP2 molecule (carrying Glubeta69) complexed with class II associated invariant chain derived peptide (CLIP) and compared it with the form carrying Lys at beta69 (HLA-DP2K69). Major changes between the two models were observed in the shape and charge distribution of pocket 4 and of the nearby pocket 6. Consequently, we analyzed in detail the peptide-binding specificities of both HLA-DP molecules expressed as recombinant proteins. We first determined that the minimum peptide-binding core of CLIP for both HLA-DP2 and DP2K69 is represented by nine aminoacids corresponding to the sequence 91-99 of invariant chain (Ii). We then assessed the peptide-binding specificities of the two pockets and determined the role of position beta69, using competition tests with the Ii-derived peptide CLIP and its mutated forms carrying all the aminoacidic substitutions in P4 and P6. Pocket 4 of HLA-DP2 showed high affinity for positively charged, aromatic, and polar residues, whereas aliphatic residues were disfavored. Pocket 4 of the DP2K69 variant showed a reduced aminoacid selectivity with aromatic residues most preferred. Pocket 6 of HLA-DP2 showed high affinity for aromatic residues, which was increased in DP2K69 and extended to arginine. Finally, we used the experimental data to determine the best molecular-modeling approach for assessing aminoacid selectivity of the two pockets. The results with best predictive value were obtained when single aminoacids were evaluated inside each single pocket, thus, reducing the influence of the overall peptide/ major histocompatibility complex interaction. In conclusion, the HLA-DPbeta69 polymorphism plays a fundamental role in the peptide-binding selectivity of HLA-DP. Furthermore, as this polymorphism is the main change in the pocket 4 area of HLA-DP, it could represent a supertype among HLA-DP molecules significantly contributing to the selection of epitopes presented in the context of this HLA isotype.

Functional analysis of HLA-DP polymorphism: a crucial role for DPbeta residues 9, 11, 35, 55, 56, 69 and 84-87 in T cell allorecognition and peptide binding

The information available on the specific function of HLA-DP and the structure-function relationships is very limited. Here, single amino acid substitutions of HLA-DPB1*02012 have been used to analyze the role of polymorphic residues of the DPbeta1 domain on DP-mediated T cell allorecognition and peptide binding. Using a panel of specific anti-HLA-DP mAb, we identified the HLA-DP residues involved in the recognition by these mAb, with a crucial role for DPbeta56 for most of the mAb assayed. Individual substitutions at residues 9, 11, 35, 55, 56 and 69 completely abrogated T cell recognition mediated by two different HLA-DPw2-allospecific T cell clones (8.3 and 8.9). Interestingly single changes at positions 9, 11, 35 and 55 of HLA-DPbeta also altered the binding of peptides AAII(12-27) and IIP(53-65), natural ligands of the HLA-DPB1*02012 molecule. Individual changes at residues located in pocket 1 (84, 85, 86 and 87 from HLA-DPbeta) led to a partial reduction in cytotoxic T lymphocyte-mediated lysis and also partially affected peptide binding. However, the simultaneous substitution of these positions completely abolished both T cell allorecognition and peptide binding, suggesting a major role for polymorphisms at pocket 1 in HLA-DP function. Molecular modeling, used to predict changes induced by amino acid substitutions, supported the functional data. Taken together, these results strongly suggest that polymorphic residues 84, 85, 86 and 87 at pocket 1, residues 9, 35 and 55 at pocket 9, and residues 11 and 69 at pockets 6 and 4 respectively play a key role in HLA-DP function, probably by modifying the way the peptide is bound within the groove of HLA-DP2 and determining changes in the conformation of the MHC-peptide complex recognized by the TCR.

Quantifying recruitment of cytosolic peptides for HLA class I presentation: impact of TAP transport

MHC class I ligands are recruited from the cytosolic peptide pool, whose size is likely to depend on the balance between peptide generation by the proteasome and peptide degradation by downstream peptidases. We asked what fraction of this pool is available for presentation, and how the size of this fraction is modulated by peptide affinity for the TAP transporters. A model epitope restricted by HLA-A2 and a series of epitope precursors with N-terminal extensions by single residues modifying TAP affinity were expressed in a system that allowed us to monitor and modulate cytosolic peptide copy numbers. We show that presentation varies strongly according to TAP affinities of the epitope precursors. The fraction of cytosolic peptides recruited for MHC presentation does not exceed 1% and is more than two logs lower for peptides with very low TAP affinities. Therefore, TAP affinity has a substantial impact on MHC class I Ag presentation.

Anti-peptide antibodies that recognize conformational differences of HLA class I intracytoplasmic domains

Rabbit antibodies were raised against both long and short peptides derived from exon 7 sequences of human leukocyte antigen (HLA) class I alpha chains; anti-A/B against a 13-mer shared by most HLA-A alpha and HLA-B alpha chains, anti-C against a 15-mer characteristic of HLA-C alpha chains, anti-ACT against a 6-mer specific to HLA-A alpha chains, and anti-CCT against a 5-mer specific to HLA-C alpha chains. Binding activity of the antibodies was determined with peptides by enzyme-linked immunoabsorbent assay (ELISA) and with HLA class I transfectants and the parental cells by FACS analysis. Anti-A/B and anti-C were to a greater or lesser extent crossreactive with the long and short peptides, whereas anti-ACT and anti-CCT were specific to the corresponding short peptides. No binding was seen for anti-ACT and anti-CCT with HLA class I transfectants, C1R-A2, C1R-B7, and 221-Cw1 and the parental cells, C1R (Cw4, E) and 721.221 (E, F). Anti-A/B and anti-C were substantially protein-reactive and the binding order was C1R-B7 > C1R-A2, 721.221 > C1R, 221-Cw1 for anti-A/B, and C1R-B7 > 721.221 > C1R, 221-Cw1, C1R-A2 for anti-C. Thus, anti-A/B and anti-C bound better to HLA-B and HLA-E rather than to HLA-A and HLA-C. Computer modeling of the three-dimensional structure of the intracytoplasmic domains demonstrated that this may be due to structural differences despite the sequence similarities.

Efficient MHC class I-independent amino-terminal trimming of epitope precursor peptides in the endoplasmic reticulum

MHC class I ligands are produced mainly by proteasomal proteolysis, in conjunction with an unknown extent of trimming by peptidases. Trimming of precursor peptides in the endoplasmic reticulum, a process postulated to be class I dependent, may substantially enhance the efficiency of antigen presentation. However, monitoring of luminal peptide processing has not so far been possible. Here we show that several precursor peptides with amino-terminal extensions are rapidly converted to HLA-A2 ligands by one or several highly efficient metallo-peptidases found on the outer surface of, but also within, microsomes. Surprisingly, luminal trimming is fully active in HLA class I- or TAP-deficient microsomes and precedes peptide association with HLA class I molecules. Trimmed peptides are rapidly depleted from, and become undetectable in, microsomes lacking the restricting class I molecules.

Allele- and temperature-dependency of in vitro HLA class I assembly

Allelic variations of in vitro HLA class I assembly have been investigated in both the absence and the presence of binding peptides by flow cytometry using human leukocyte antigen (HLA) class I alpha chains isolated by alkali treatment from cultured HLA homozygous B cells and polystyrene beads coated with anti-HLA class I alpha chain antibodies specific to the C-terminal segment (anti-HLA class I beads). The specificity of assembly was temperature dependent, while the stability of the assembled complex depended on the bound peptide. The efficiency of assembly was allele dependent and primarily ruled by the binding affinity of alpha chains with beta(2)m. Thus, an allele hierarchy could be defined for the binding of HLA-B alpha chain with beta(2)-microglobulin: B7, B18 > B35, B62 > B27, B51. Allele and temperature dependency was found in HLA class I reassembly on acid treated B cells. The HLA class I proteins, reassembled with specific single peptides, could be efficiently transferred to anti-HLA class I beads. These findings would be used to produce microspheres coupled at high surface density with oriented single-peptide loaded HLA class I molecules and also to improve the preparation efficiency of HLA class I tetramers by the use of site-specific biotinylation.

Domain interactions affecting human DNA topoisomerase I catalysis and camptothecin sensitivity

DNA topoisomerase I (Top1p) relaxes supercoiled DNA by the formation of a covalent intermediate in which the active site tyrosine is transiently bound to the severed DNA strand. The antineoplastic agent camptothecin (Cpt) specifically targets Top1p and several mutations have been isolated that render the enzyme Cpt resistant. The mutated residues, although located in different regions of the enzyme, may constitute part of the Cpt binding site. To begin identifying the structural features of DNA Top1p important for Cpt-induced cytotoxicity, we developed a novel yeast genetic screen to isolate catalytically active, yet Cpt-resistant enzymes from a pool of human top1 mutants. Among the mutations isolated were substitutions of Ser or Val for Gly363, which like the Gly363 to Cys mutation previously reported by us, suppressed the Cpt sensitivity of Top1p. In contrast, each amino-acid substitution differed in its ability to suppress the lethal phenotype and catalytic activity of a human top1 mutant top1T718A that resembles Cpt by stabilizing the covalent intermediate. Biochemical analyses and molecular modeling support a model where interactions between two conserved domains, a central "lip" region containing residue Gly363 and the residues around the active site tyrosine (Tyr723), directly affect the formation of the Cpt-binding site and enzyme catalysis.

Differential expression of heat shock protein (HSP70) mRNAs in rat cells

Heat shock treatment in PC12 cells induces the synthesis of two HSP70 transcripts of 2.55 and 3.05 kb in size, while only a 70-kDa protein is shown by SDS-PAGE. Using reverse transcription-polymerase chain reaction strategy, two mRNA species were amplified from heat-shocked PC12 cells and sequenced. Both cDNAs revealed the same open reading frame encoding a single predicted 641-amino-acid polypeptide of about 70 kDa. The two 3' untranslated regions of the two mRNAs were completely different in both length and composition. Expression of the mRNA of the two corresponding genes and that of another rat HSP70 family member was investigated in PC12, Rat1 cells, and lung fibroblasts. Northern blot analysis revealed that the 2.55- and the 3.05-kb related gene transcripts are differentially expressed in the rat cell lines tested, while the third member of the subfamily is not induced. The single-copy nature of the three genes is also confirmed by Southern blot analysis.

Augmentation of the affinity of HLA class I-binding peptides lacking primary anchor residues by manipulation of the secondary anchor residues

A direct binding assay has been used to investigate the effect of the secondary anchor residues on peptide binding to class I proteins of the major histocompatibility complex. Based on predictions from a previous chemometric approach, synthetic peptide analogues containing unnatural amino acids were synthesized and tested for B*2705 binding. Hydrophobic unnatural amino acids such as alpha-naphthyl- and cyclohexyl-alanine were found to be excellent substituents in the P3 secondary anchor position giving peptides with very high B*2705-binding affinity. The binding to B*2705 of peptides optimized for their secondary anchor residues, but lacking one of the P2 or P9 primary anchor residues was also investigated. Most such peptides did not bind, but one peptide, lacking the P2 Arg residue generally considered essential for binding to all B27 subtypes, was found to bind quite strongly. These findings demonstrate that peptide binding to class I proteins is due to a combination of all the anchor residues, which may be occupied also by unnatural amino acids-a necessary step towards the development of peptidic or non-peptidic antagonists for immunomodulation.

Differences in peptide-binding specificity of two ankylosing spondylitis-associated HLA-B27 subtypes

Two HLA-B27 subtypes, B*2702 and B*2705, both associated with ankylosing spondylitis, were tested for binding affinity with a panel of polyalanine model nonapeptides carrying Arg at position 2 (P2) and a series of different amino acids at position 9 (P9). The alpha chains were isolated from BTB(B*2705), C1R/B*2702 (a B*2702 transfectant cell line) and from the NW (B*2702) cell line that has a peculiar peptide presentation behavior. Peptide binding was measured by the HLA alpha chain refolding assay. The results obtained show that: 1) Peptides with basic residues (Arg and Lys) and also aliphatic (Leu) and aromatic (Phe and Tyr) peptides at P9 have a similar high affinity in the binding to B*2705; 2) B*2702 binds well to P9 aliphatic and aromatic peptides but only very weakly to P9 basic peptides. Since both B*2702 and B*2705 are associated with AS the presumed arthritogenic peptide is hypothesized to have an aromatic or aliphatic residue at position 9. Peptides with basic residues in this position would be excluded as candidates because of their low binding affinity with B*2702.

Exploring myelin basic protein for HLA class I-binding sequences

In view of the increasing evidence of the involvement of CD8+ T cells in the pathogenesis of multiple sclerosis (MS), we have scanned the sequence of the myelin basic protein (MBP), using 162 overlapping nonapeptides, for HLA-class I binding sites. Peptide binding was measured using the recently reported HLA class I alpha-chain-refolding assay, and the following HLA allelic products were analyzed: HLA-A2 (*0201, *0204), B27 (*2705), B35, B51 and B62. A considerable number of binding peptides were distinguished for each of the allelic products tested. In addition, three interesting points emerged. The first was the identification of several binding peptides which did not contain the known anchor motifs. The second was the evidence that several peptides showed a promiscuous binding profile, being able to bind to different HLA class I molecules that were either allelic or non allelic. The third was that in several cases two consecutive peptides could bind to the same HLA molecule.

The peptide-binding specificity of HLA-B27 subtype (B*2705) analyzed by the use of polyalanine model peptides

Model peptides have been used to quantitate the effect on HLA-B*2705 binding of the spacing between primary anchor residues, the type of amino acid accepted in the P9 anchor position, and the type of amino acid accepted in the "secondary anchor positions" P3 and P7. Peptide binding was measured by the HLA class I alpha-chain-refolding assay. The results obtained show that (a) Among the model peptides differing in the spacing between anchor residues, the nonamer with Arg in P2 and Lys in P9 (R2, K9) has the maximum binding with B*2705 molecule. The decamer, with an extra Ala inserted between Arg and Lys (R2, K10), has much lower binding, and still lower binding is observed for the octamer, where an Ala is removed (R2, K8). (b) Besides the "classic" Lys and Arg, several other aminoacids such as Tyr, Leu, Ala, and Gln can be accepted in P9, but with significant differences in binding affinity. (c) Different amino acids in P3 have an influence on peptide binding. Trp and Phe have a favorable influence, whereas Lys and Val appear to hinder the binding. Some variations are seen also for different amino acids in P7.

The peptide binding specificity of HLA-B27 subtypes

Five HLA-B27 subtypes, B*2701, B*2703, B*2704, B*2705, and B*2706, were tested for direct binding with twenty-six synthetic nonapeptides carrying the primary anchor residue motifs (combination of amino residues at positions 2 and 9) relevant to B*2705. The peptide sequences were derived from human HSP89 alpha, P53 and MBP. The alpha chains were immunospecifically isolated from LH (B*2701), CH (B*2703), WE1 (B*2704), BTB (B*2705), and LIE (B*2706) cells and their peptide binding was measured by the HLA class I alpha chain refolding assay. The data obtained indicated that the B27 subtypes tested can bind a common set of peptides carrying several different anchor residue motifs. The motifs, R-K and R-R, reported for B*2705 and a new motif H-R were accepted by B*2703, B*2704, and B*2706, but not by B*2701. However, other motifs, including known B*2702 and/or B*2705 motifs, R-H, R-L, R-A, and R-F, and a new motif found here, R-G, were apparently accepted by all B27 subtypes tested. The observed cross-peptide binding in the B27 subgroup is compatible with the so-called arthritogenic peptide hypothesis in the pathogenesis of ankylosing spondylitis.

HLA-A2-binding peptides cross-react not only within the A2 subgroup but also with other HLA-A-locus allelic products

Seven A2-binding peptides were tested by the HLA class I alpha-chain refolding assay previously described for their direct binding to HLA class I alpha chains derived from a panel of 18 HLA-homozygous B-cell lines of various HLA specificities, including four A2 subtypes: A*0201, A*0204, A*0205, and A*0206. All but one test peptide possessed the major anchor residue motifs, L-V, L-L, or I-L, of A2(A*0201)/A2(A*0205)-binding peptides or the closely related motifs, I-V or V-V. This cell panel analysis confirmed the high A2 allele specificity of the test peptides, but also revealed the existence of a broad cross-binding within the A2 subgroup. Most peptides bound to the alpha chains of the A2 subtypes tested, although their binding patterns showed differences. Furthermore, the A2-binding peptides carrying the I-V or V-V motif were found to cross-react also outside of the A2 subtypes, probably with A24, A26, A28, and A29. Other A-locus allelic products, A1, A3, A11, A30, and A31, and the B-locus allelic products carried by the cells tested were essentially negative, although a few exceptions were seen.

5-Methylcytosine in genes with methylation-dependent regulation

An asymmetric distribution of deoxy-5-methylcytidylic acid-inhibiting restriction sites (dcm-sites) takes place in ten human genes regulated by 5-methylcytosine. These genes are dcm-site enriched upstream and dcm-site poor downstream. Along them, there is a scattering of hypermethylatable introns and hypomethylatable exons with a common code: the 5mCpG dinucleotides characterize promoters; Gp5mCs characterize introns; Tp5mCs and Cp5mCs are in small concentrations in exons. Housekeeping genes contain more dcm-sites when compared with tissue-specific genes. This depends on the higher number of dcm-sites in their promoters and introns. In exons, the relatively lower number of dcm-sites is almost the same in both housekeeping and tissue-specific genes. Going from 5' to 3', the average frequency of occurrence of these sites per nucleotide units decreases in introns and increases in exons. This difference is highly discriminated for tissue-specific and less discriminated for housekeeping genes.

HLA class I binding of synthetic nonamer peptides carrying major anchor residue motifs of HLA-B27 (B*2705)-binding peptides

Eight nonamer peptides that comply with the major anchor residue motifs (the combination of amino acid residues at positions 2 and 9), R - K and R - R, of HLA-B27 (B*2705)-binding peptides were synthesized and tested for their direct binding to HLA class I alpha chains by the HLA class I alpha chain refolding assay previously described. One was a known B27 (B*2705)-binding heat shock protein peptide, HSP89 alpha (201-209), and the other seven were derived from the sequence of wild-type P53, a human tumor suppressor protein. A total of 36 HLA class I allospecificities were tested. HSP89 alpha (201-209) and two P53 peptides, P53 (362-370) and P53 (378-386), all possessing the motif R - K, bound strongly to B27 (B*2705) alpha chains. A weak binding was seen for P53 (272-280) and P53 (334-342), both showing the motif R - R. Most of these B27-binding peptides were found to bind to A3 alpha chains as well. In addition, P53 (173-181) and P53 (334-342), both with the R - R motif, showed substantial binding with A31 alpha chains. All the peptides carrying the motif R - K also showed weak binding with A31 alpha chains. The remaining two peptides, P53 (201-209) and P53 (282-290), with the motif R - R, did not show significant binding with any of the alpha chains tested. This study demonstrates both the specificity of peptide binding to a given HLA allelic product and the occurrence of cross-peptide-binding between the allelic products of different HLA loci.

Unfolded HLA class I alpha chains and their use in an assay of HLA class-I-peptide binding

Unfolded HLA class I alpha chains were isolated from B-cell lysates by alkaline denaturation and subsequent gel filtration and used for the detection of HLA class-I-peptide binding. Binding to specific peptides in the presence of excess beta 2-microglobulin induced the unfolded alpha chains to refold and acquire a conformation that is specific to folded alpha chains. This conformational change was measured by a specific RIA that involves inhibition of the binding of 125I-labeled HLA-A2 alpha/beta dimers and rabbit anti-HLA-B7 serum absorbed with beta 2-microglobulin. This assay procedure does not require labeling of either test peptides or test class I proteins and does not seem to have specificity degeneracy. It is applicable to the detection of peptide binding by all HLA class I allelic proteins. Evaluation of the assay conditions and HLA allelic specificity of the peptide binding defined by the use of synthetic peptides are described here, including the technical details, specificity, and reproducibility.

Global changes in gene expression in Escherichia coli K12 induced by bacteriophage Mu Gem protein

We have studied the growth properties of some Mu lysogens with respect to the non-lysogenic strain and have observed that the division time in minimal medium was increased over 4-fold when the bacteria carried the prophage mutated in the gem gene (Mu gem3). Since this phage gene has previously been shown to be involved in modulation of expression of host genes, we have analysed the proteins extracted from lysogens and non-lysogens as a rapid assay of global gene expression. The pattern of proteins extracted showed marked quantitative variations between non-lysogens, lysogens for wild-type Mu and lysogens for phage Mu gem3. These effects were no longer as evident when the strains were grown in rich medium. This dramatic change in the physiological state of the lysogenic strain versus the non-lysogenic in particular growth conditions extends the concept of lysogeny. For many years, the prophage has been considered only as a potentially lethal factor, while here it also appears as a genetic element capable of profoundly modifying host biology.

Mode of action of the schistosomicide hycanthone: site of DNA alkylation

Condensation of hycanthone N-methylcarbamate (HNMC) with deoxyguanosine (dG) furnished a mixture of the N-1 and N2 adducts which were purified and characterized as their acetates. Condensation of HNMC with thymidine (T) gave the N-3 adduct in poor yield. Adenosine (A) and cytidine (C) did not react with HNMC. Incubation of schistosomes with either [3H]hycanthone (HC) or [3H]HNMC furnished DNA to which [3H]HC was covalently bound. The alkylated DNA was degraded enzymically and the radiolabeled nucleosides were separated using HPLC. Two major peaks were observed which coincided in retention time with the synthetic N-1 and N2 alkylated dG. Alkylated T was absent. Thus, the site of alkylation of DNA by either HC or HNMC is dG.

Interleukin-1 production by a cloned line of human monocyte-like cells (CM-SM). Correlation with state of differentiation

Interleukin-1 (IL-1) production by the human monocyte-like cloned cell line CM-SM has been investigated as a function of the state of cell differentiation. CM-SM cells were induced to differentiate along the monocyte-macrophage lineage by bacterial lipopolysaccharides (LPS) or by 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Cell differentiation was studied by various morphological, functional, cytochemical, and immunological variables, whereas IL-1 activity in the supernatants was measured by the lectin-primed thymocyte proliferation assay. Unstimulated CM-SM cells constitutively produced small amounts of IL-1, and most of the cells appeared relatively undifferentiated. LPS induced cell differentiation, but the effect was reversible, and the cells, in general, did not acquire a capacity for phagocytosis. IL-1 levels were increased about 10-fold over the controls. TPA induced further cell differentiation to macrophage-like cells capable of phagocytosis. IL-1 activity could not be measured directly in the supernatants owing to the synergistic effect of TPA in the assay system. Unequivocal removal of the phorbol was not achieved, but the data indicated that the 'real' levels of IL-1 in the TPA-induced cultures were not significantly higher than those from LPS-induced cultures.

Growth factors that stimulate human granulocyte-macrophage colony formation produced by the cell line CM-S

CM-S is an autonomous cell line of human hemopoietic precursor cells inducible to monocyte-macrophage differentiation in response to appropriate inducing agents. CM-S cells produce factors that stimulate their own growth and proliferation, and are also capable of stimulating clonal proliferation of human, but not mouse, monocytic and granulocytic bone marrow progenitor cells in viscous medium. Preliminary purification steps have demonstrated at least two species, one of which (MW 30,000-50,000) retains both these activities, while the other (MW less than or equal to 10,000) apparently retains only the autostimulatory activity. CM-S cells could thus be a useful source for the purification of human colony stimulating factors (CSFs). CM-S cells also respond to factors present in human placenta conditioned medium, known to contain human CSF. This suggests that CM-S cells could provide a homogeneous target cell population for testing CSFs from other human sources.

Constitutive production of Interleukin-1 by the human continuous cell line, CM-S

Supernatants from the human continuous cell line, CM-S, have been tested for Interleukin-1 (IL-1) activity and found to constitutively elaborate this factor. The CM-S-produced IL-1 activity has been partially purified and shown to be similar to IL-1 produced by human and mouse peripheral blood macrophages. To the best of our knowledge this is the first continuous human cell line reported that produces this monokine.

Antigenic sites on mouse 2.5S nerve growth factor

Cyanogen bromide and tryptic peptides of mouse 2.5S Nerve Growth Factor (NGF) have been used to inhibit competitively binding of rabbit antiserum anti-NGF to native NGF in a solid-phase radioimmunoassay. The results showed that the larger of the two peptides obtained by cyanogen bromide cleavage (amino-acid residues 10-118) was indistinguishable from NGF in this respect, whereas the smaller N-terminal peptide (residues 1-9) was virtually non-inhibitory. Ten peptides were purified from a tryptic digest of the larger cyanogen bromide fragment. One of them, peptide G7 (residues 58-59, 60-69, 104-114, linked by disulfide bridges), was capable of almost full inhibition of binding, though only when used at a concentration about 100 times higher than that necessary to get the same effect with NGF. One other peptide, G10-H1 (residues 70-74), showed some inhibition at relatively high concentrations, but the majority of peptides, including peptide DE-5 which has been shown to be active in the NGF bioassay, were essentially non-inhibitory. A significant co-operative effect was seen when peptides G7 and G10-H1 were used in conjunction. No such effects were observed with any other combination tested.

Monoclonal antibodies against mouse nerve growth factor produced by somatic cell hybrids

Spleen leukocytes from rats and mice immunized against mouse 2.5S nerve growth factor (NGF) and peripheral blood leukocytes from rabbits hyper-immunized against the same antigen were fused with the mouse plasmacytoma P3X63Ag8. Hybridomas were screened by immunological assays (micro-complement fixation test and solid phase radioimmunoassay) for production of antibodies that reacted with NGF. Significant variations were seen between culture fluids from different hybrid cells. In addition, most but not all hybridoma antibodies that reacted immunologically with NGF prevented neurite outgrowth from 8-day chick embryo sensory ganglia explants after binding to NGF. These results suggest that the hybridoma antibodies produced by the different clones react with different antigenic sites on the NGF molecule.

Nerve growth factor may stimulate either division or differentiation of cloned C1300 neuroblastoma cells in serum-free cultures

Two clones of mouse C1300 neuroblastoma cells (clones NB1R and NB6R) bind mouse 2.5S Nerve Growth Factor (NGF) in vitro. The ligand is then capped and internalized by the cells. This step requires active cell processing. In serum-free or low serum conditions, clear effects of NGF are seen with both clones. Cultured NB1R cells are stimulated, after a lag interval of a few hours, to synthesize DNA and to proliferate, whereas NB6R cells are stimulated to cell differentiation and maintain viability under these conditions much longer than similar cultures in the absence of NGF. Stimulation of clone NB1R occurs within an optimal dose concentration of the same order as that used in the Levi-Montalcini bioassay with 8-day-old chick embryo-sensitive ganglia; the effects on clone NB6R, however, need higher NGF concentrations. Both effects are protein-specific since they are inhibited in the presence of added anti-NGF antibodies. This system could provide a convenient means to study the control of cell division in susceptible malignant neuroblastoma clones and to correlate NGF binding to receptors and biological activity.

Protection of mice against syngeneic C1300 neuroblastoma challenge by immunization with membranes of C1300 neuroblastoma cells

Male A/J mice 2-3 months old were inoculated sc with membranes from syngeneic C1300 neuroblastoma cells (clone NB6R) in complete Freund's adjuvant. Significant immunoprophylaxis was noted in the sensitized mice upon sc challenge with viable NB6R cells. During the experiment (60 days from viable cell challenge), each control mouse developed a palpable tumor and died within 50 days. Complete protection was obtained with a program of 4 inoculations of NB6R cell membranes. Each mouse given only 1 inoculation of NB6R cell membranes developed a palpable tumor, but afer 60 days only 1 mouse in 7 had died, which indicated a significant degree of protection. With in vitro tests of lymphocyte proliferation, rosette formation, and complement fixation, it was shown that these mice had mounted both cellular and humoral immune response against the tumor cells.