Effects of various cooking conditions on acrylamide formation in rolled patty

In this study on acrylamide formation, the effects of the type of frying oil, frying period and covering with egg during frying of a rolled patty (a traditional Turkish carbohydrate-rich food) were investigated. The differences between frying periods were statistically significant for each oil (p < 0.01). For comparable frying periods, the maximum acrylamide content was found in the rolled patties fried with sunflower oil, and the minimum acrylamide content was found in the rolled patties fried with corn oil. A decrease of 39-65% in acrylamide formation in the rolled patties covered with egg was found for each of the three types of oil. In addition, a high linear correlation (R > 0.90) was found between L (light) values and acrylamide amounts.

Foxp3 processing by proprotein convertases and control of regulatory T cell function

Foxp3 is a 47-kDa transcription factor central to regulatory T cell (Treg) function. The importance of Foxp3(+) Tregs in controlling self-reactive T cells and preventing autoimmunity is well established. Our analysis of Foxp3 expression in natural Tregs led to identification of a shorter 41-kDa Foxp3 species in activated Tregs, indicating that Foxp3 may be processed by proteolytic cleavage upon cell activation. Searches of murine and human Foxp3 sequences for potential cleavage sites responsible for the generation of the short Foxp3 species revealed the presence of two RXXR proprotein convertase (PC) motifs, (48)RDLR(51) and (414)RKKR(417), located near the N- and C-terminal ends, respectively. We show, using retroviral expression of Foxp3 in CD4(+) T cells, that Foxp3 is cleaved at both the N- and C-terminal RXXR sites and that mutagenesis of the RXXR motif prevents cleavage. The cleaved forms of Foxp3 are found in the chromatin fraction but not in nuclear or cytoplasmic extracts. CD4(+) T cells expressing Foxp3 species engineered to mimic N-terminally, C-terminally, or N- and C-terminally cleaved Foxp3 forms are functionally distinct, as indicated by differences in expression of key Treg genes, such as interleukin-10 and cytotoxic T-lymphocyte antigen 4 (CTLA-4). In addition, CD4(+) cells expressing C-cleaved Foxp3 are superior to those that express WT Foxp3 in preventing experimental colitis. Coexpression of Foxp3 with PC1 or PC7 results in cleavage of the Foxp3 C terminus. The mechanism by which Foxp3 is processed likely extends to other members of the FoxP subfamily, because Foxp1 and Foxp2 also have N-terminal RXXR proteolytic cleavage motifs at similar locations to Foxp3. Our results indicate that the generation of fully functionally competent Tregs is complex and dependent on the generation of multiple forms of Foxp3 that have differing effects on Treg cytokine production and suppressive function.

Deacetylase inhibition promotes the generation and function of regulatory T cells

Histone/protein deacetylases (HDACs) regulate chromatin remodeling and gene expression as well as the functions of more than 50 transcription factors and nonhistone proteins. We found that administration of an HDAC inhibitor (HDACi) in vivo increased Foxp3 gene expression, as well as the production and suppressive function of regulatory T cells (T(reg) cells). Although T(reg) cells express multiple HDACs, HDAC9 proved particularly important in regulating Foxp3-dependent suppression. Optimal T(reg) function required acetylation of several lysines in the forkhead domain of Foxp3, and Foxp3 acetylation enhanced binding of Foxp3 to the Il2 promoter and suppressed endogenous IL-2 production. HDACi therapy in vivo enhanced T(reg)-mediated suppression of homeostatic proliferation, decreased inflammatory bowel disease through T(reg)-dependent effects, and, in conjunction with a short course of low-dose rapamycin, induced permanent, T(reg)-dependent cardiac and islet allograft survival and donor-specific allograft tolerance. Our data show that use of HDACi allows the beneficial pharmacologic enhancement of both the numbers and suppressive function of Foxp3(+) T(reg) cells.

Histone deacetylase inhibitors and transplantation

Simply detecting the presence or absence of Foxp3, a transcription factor characteristic of naturally occurring CD4+ CD25+ regulatory T cells (Tregs), now appears of minimal value in predicting the outcome of immunologic responses, since dividing human CD4+ effector T cells can induce Foxp3 without attaining repressive functions, and additional molecular interactions, as well epigenetic events, affect Foxp3-dependent Treg functions in humans and mice. Experimentally, in vivo and in vitro studies show histone deacetylase inhibitors (HDACi) can enhance the numbers and suppressive function of regulatory T cells (Tregs) by promoting Foxp3+ cell production, enhancing chromatin remodeling within Tregs, and inducing acetylation of Foxp3 protein itself. Human studies consistent with a role for HDACi in controlling Fox3-dependent Treg functions are also available. We review these molecular interactions and how they may be exploited therapeutically to enhance Treg-dependent functions, including post-transplantation.

Alloimmunity in primate heart recipients with CD154 blockade: evidence for alternative costimulation mechanisms

BACKGROUND

CD154 mediates key facets of humoral and cellular immunity to alloantigens, and is tolerogenic to influenza antigens in primates. Barriers to CD154-based tolerance induction for primate cardiac allografts have not previously been defined.

METHODS

Heterotopic cardiac allograft outcomes in cynomolgus monkeys treated with a CD154 inhibitor, IDEC-131 (n=27), were compared to no treatment (n=4) or cyclosporine A (n=6).

RESULTS

CD154 blockade significantly prolonged median allograft survival, from 6.2 (range 6, 7, n=4) days in untreated controls, to 39 (8,112, n=16) days with intensive monotherapy and 93 (>25, 386; n=3) days with added antithymocyte globulin (ATG), but did not yield tolerance. Alloantibody production was delayed but not prevented by IDEC-131 alone or with ATG, and was exacerbated by infusion of donor bone marrow (n=8). Expression of ICOS was prominent in graft infiltrating lymphocytes, and preceded elaboration of antidonor antibody and vasculopathy.

CONCLUSION

CD154 monotherapy modulates primate cardiac alloimmunity, but does not readily induce tolerance. Targeting alternative costimulation pathways, including ICOS, may facilitate tolerance induction based on CD154 blockade.

Recruitment of Foxp3+ T regulatory cells mediating allograft tolerance depends on the CCR4 chemokine receptor

Although certain chemokines and their receptors guide homeostatic recirculation of T cells and others promote recruitment of activated T cells to inflammatory sites, little is known of the mechanisms underlying a third function, migration of Foxp3⁺ regulatory T (T reg) cells to sites where they maintain unresponsiveness. We studied how T reg cells are recruited to cardiac allografts in recipients tolerized with CD154 monoclonal antibody (mAb) plus donor-specific transfusion (DST). Real-time polymerase chain reaction showed that intragraft Foxp3 levels in tolerized recipients were ∼100-fold higher than rejecting allografts or allografts associated with other therapies inducing prolonged survival but not tolerance. Foxp3⁺ cells were essential for tolerance because pretransplant thymectomy or peritransplant depletion of CD25⁺ cells prevented long-term survival, as did CD25 mAb therapy in well-functioning allografts after CD154/DST therapy. Analysis of multiple chemokine pathways showed that tolerance was accompanied by intragraft up-regulation of CCR4 and one of its ligands, macrophage-derived chemokine (CCL22), and that tolerance induction could not be achieved in CCR4^−/− recipients. We conclude that Foxp3 expression is specifically up-regulated within allografts of mice displaying donor-specific tolerance, that recruitment of Foxp3-expressing T reg cells to an allograft tissue is dependent on the chemokine receptor, CCR4, and that, in the absence of such recruitment, tolerizing strategies such as CD154 mAb therapy are ineffectual.

Systemic Transforming Growth Factor-??1 Gene Therapy Induces Foxp3+ Regulatory Cells, Restores Self-Tolerance, and Facilitates Regeneration Of Beta Cell Function in Overtly Diabetic Nonobese Diabetic Mice

BACKGROUND

Type 1 diabetes results from auto-aggressive T-cell-mediated destruction of beta cells of the pancreas. Recent data suggest that restoration of self-tolerance may facilitate islet-cell regeneration/recovery. In view of the immunoregulatory activity of transforming growth factor (TGF)-beta1, we investigated whether systemic TGF-beta1 gene therapy blocks islet destructive autoimmunity and facilitates regeneration of beta-cell function in overtly diabetic nonobese diabetic (NOD) mice.

METHODS

We used site-directed mutagenesis to create cysteine to serine mutation at sites 224 and 226 and constructed a replication deficient adenovirus (Ad) vector encoding active form of human TGF-beta1 (Ad-hTGF-beta1). Overtly diabetic NOD mice received intravenous injection of Ad-hTGF-beta1. Seven to 14 days after the injection, the mice received transplants with 500 syngeneic islets under the kidney capsule. Islet-graft survival and regeneration of endogenous beta-cell function were examined.

RESULTS

Syngeneic islet grafts failed by day 17 in all untreated mice, whereas Ad-hTGF-beta1 therapy prolonged survival of islet grafts. Islet grafts from treated mice showed well-preserved islets with a peri-islet infiltrate primarily of CD4+ T cells and expression of CD25 and Foxp3. Systemic TGF-beta1 gene therapy was associated with islet regeneration in the native pancreas. Native pancreas of treated mice revealed islets staining strongly for insulin. Similar to what was found in the syngeneic islet graft, there were well-demarcated peri-islet infiltrates that were positive for CD4, TGF-beta1, and Foxp3.

CONCLUSIONS

Our data demonstrate that systemic TGF-beta1 gene therapy blocks islet destructive autoimmunity, facilitates islet regeneration, and cures diabetes in diabetic NOD mice.

Disruption of the ICOS-B7RP-1 costimulatory pathway leads to enhanced hepatic immunopathology and increased gamma interferon production by CD4 T cells in murine schistosomiasis

Morbidity and mortality in schistosomiasis are largely due to an immune response mediated by CD4 T lymphocytes. Since lymphocyte activation is shaped by costimulatory signals, the specific functions of different costimulatory pathways are of increasing interest. We now examined the role of the inducible costimulatory molecule (ICOS) and its ligand B7-related protein 1 (B7RP-1) in the experimental murine schistosome infection by blocking this costimulatory pathway with monoclonal antibody against ICOS, administered daily by intraperitoneal injection during the patent phase of the disease. The treated mice exhibited enhanced hepatic immunopathology characterized by enlarged egg granulomas and pronounced parenchymal inflammation with hepatocellular necrosis, resulting in elevated liver enzyme levels in serum. Most strikingly, there was a sharp increase in gamma interferon (IFN-gamma) production by schistosome egg antigen-stimulated granuloma cells, bulk mesenteric lymph node (MLN) cells, and purified MLN CD4 T cells, which contrasted with a more discreet change in the Th2-type cytokines interleukin 4 (IL-4) and IL-10. These findings suggest that the ICOS-B7RP-1 costimulatory pathway serves primarily to control IFN-gamma production, thereby promoting a cytokine environment conducive to limited hepatic damage.

Programmed death-1 targeting can promote allograft survival

The recently identified CD28 homolog and costimulatory molecule programmed death-1 (PD-1) and its ligands, PD-L1 and PD-L2, which are homologs of B7, constitute an inhibitory regulatory pathway of potential therapeutic use in immune-mediated diseases. We examined the expression and functions of PD-1 and its ligands in experimental cardiac allograft rejection. In initial studies, we found that most normal tissues and cardiac isografts had minimal expression of PD-1, PD-L1, or PD-L2, but intragraft induction of all three molecules occurred during development of cardiac allograft rejection. Intragraft expression of all three genes was maintained despite therapy with cyclosporin A or rapamycin, but was prevented in the early posttransplant period by costimulation blockade using CD154 or anti-inducible costimulator mAb. We prepared PD-L1.Ig and PD-L2.Ig fusion proteins and showed that each bound to activated PD-1(+) T cells and inhibited T cell functions in vitro, thereby allowing us to test the effects of PD-1 targeting on allograft survival in vivo. Neither agent alone modulated allograft rejection in wild-type recipients. However, use of PD-L1.Ig administration in CD28(-/-) recipients, or in conjunction with immunosuppression in fully MHC-disparate combinations, markedly prolonged cardiac allograft survival, in some cases causing permanent engraftment, and was accompanied by reduced intragraft expression of IFN-gamma and IFN-gamma-induced chemokines. PD-L1.Ig use also prevented development of transplant arteriosclerosis post-CD154 mAb therapy. These data show that when combined with limited immunosuppression, or in the context of submaximal TCR or costimulatory signals, targeting of PD-1 can block allograft rejection and modulate T and B cell-dependent pathologic immune responses in vivo.

The costimulatory molecule ICOS plays an important role in the immunopathogenesis of EAE

The inducible costimulatory molecule (ICOS) is expressed on activated T cells and participates in a variety of important immunoregulatory functions. After the induction of experimental allergic encephalomyelitis in SJL mice with proteolipid protein (PLP), brain ICOS mRNA and protein were up-regulated on infiltrating CD3+ T cells before disease onset. ICOS blockade during the efferent immune response (9-20 days after immunization) abrogated disease, but blockade during antigen priming (1-10 days after immunization) exacerbated disease. Upon culture with PLP and compared with immunized controls, splenocytes produced either decreased interferon-gamma (IFN-gamma, in efferent blockade) or excessive IFN-gamma (in priming blockade). PLP-specific immunoglobulin G1 was decreased in animals treated with anti-ICOS during antigen priming, but not in other groups.

Importance of ICOS-B7RP-1 costimulation in acute and chronic allograft rejection

Primary T cell activation requires B7-CD28 and CD40-CD154 costimulation, but effector T cell functions are considered to be largely independent of these costimulatory pathways. Although blockade of costimulation with cytolytic T lymphocyte-associated antigen 4-immunoglobulin (CTLA-4-Ig) or monoclonal antibody (mAb) to CD154 prolongs allograft survival, chronic rejection follows, which suggests that additional key costimulatory pathways are active in vivo. We found that both antibody to inducible costimulator (anti-ICOS) and an ICOS-Ig fusion protein suppressed intragraft T cell activation and cytokine expression and prolonged allograft survival in a manner similar to that in ICOS-/- allograft recipients. The combination of anti-ICOS therapy and cyclosporin A led to permanent engraftment. In addition, ICOS-B7RP-1 costimulation was required for the development of chronic rejection after CD40-CD154 blockade. These data demonstrate a key role for the ICOS-B7RP-1 pathway in acute and chronic rejection and highlight the benefits of targeting this pathway in combination with the use of conventional immunosuppressive agent.

The 5' flanking region of the human bone morphogenetic protein-7 gene

We describe here the cloning and characterization of the 5' flanking region of the human Bone Morphogenetic Protein-7 (BMP-7) gene from a 3.3 kb genomic DNA fragment. Functional analysis by transient transfection using the luciferase reporter gene indicated that this region had a low basal promoter activity in human Wilm's tumor derived renal (G401) and rat osteoblast (ROS 17/2.8) cell lines. Sequential deletion analysis of the promoter revealed sequences whose presence correlated with decreased expression of the reporter gene. Coexpression of transcription factors involved in epithelial/mesenchymal interactions during kidney and eye development dramatically stimulated the expression of the reporter gene from the putative BMP-7 promoter. Finally, a subset of agents that upregulated the expression of the reporter gene from the cloned promoter were also shown to increase the expression of the endogenous BMP-7 in G401 and ROS cell lines in vitro.

Osteogenic protein-1 mRNA in the uterine endometrium

OP-1, a bone morphogenetic protein (BMP) in the TGF-beta superfamily, is expressed at high levels in the kidney and in the endometrium of the uterus of non-pregnant mice. During pregnancy the OP-1 mRNA in the endometrium rapidly declined at 4 dpc. Thereafter, OP-1 transcripts were detected in the trophoblastic giant cells of the placenta and the fetal tissues. The uterine OP-1 mRNA downregulation could be mimicked by administration of 17 beta-estradiol but not by progesterone to non-pregnant animals. In contrast, OP-1 mRNA expression in kidneys and ovaries was not affected by pregnancy or estrogen treatment. The selective effect of estrogen on OP-1 mRNA in the uterus suggests that OP-1 expression is regulated by tissue specific mechanisms.

Expression pattern of osteogenic protein-1 (bone morphogenetic protein-7) in human and mouse development

Osteogenic protein-1 (OP-1; BMP-7) is a member of the bone morphogenetic protein subfamily. Because members of the TGF-beta superfamily have a role in tissue development, the distribution of OP-1 expression in developing human embryos (5-8 gestational weeks) and fetuses (8-14 gestational weeks) and mouse (9.5-17.5 gestational days) fetuses was examined. Northern hybridization with specific OP-1 probes revealed two mRNA species of 4 and 2.2 KB. Highest levels of OP-1 mRNA were found in human fetal kidney and heart between 12-14 weeks of gestation. By in situ hybridization, the OP-1 transcripts were found in various tissues, i.e., the ectodermal epithelium of the mouse fore- and hindlimbs, heart, teeth, intestinal epithelium, perichondrium, hypertrophic chondrocytes, and periosteum/osteoblast layer of developing human bones. In kidneys, transcripts were first detected in the epithelium of the branching uretheric buds, whereas at later stages glomeruli were the major site of OP-1 mRNA accumulation. These data suggest that, although OP-1 has been isolated from bone matrix, it may have additional regulatory roles in the morphogenesis and/or function of the kidney, limb bud, tooth, heart, and intestine.

Osteogenic protein-2. A new member of the transforming growth factor-beta superfamily expressed early in embryogenesis

Osteogenic protein-2, OP-2, a new member of the transforming growth factor-beta (TGF-beta) superfamily, closely related to the osteogenic/bone morphogenetic proteins, was discovered in mouse embryo and human hippocampus cDNA libraries. The TGF-beta domain of OP-2 shows 74% identity to OP-1, 75% to Vgr-1, and 76% to BMP-5, hence OP-2 may also have bone inductive activity. The genomic locus of OP-2 has seven exons, like OP-1, and spans more than 27 kilobases (kb). In the C-terminal TGF-beta domain, OP-2 has a unique additional cysteine. Mouse embryos express relatively high levels of OP-2 mRNA at 8 days, two species of 3 and 5 kb. A careful study of mRNA expression of the osteogenic proteins in specific organs revealed discrete mRNA species for BMP-3, BMP-4, BMP-5, and BMP-6/Vgr-1 in lung or liver of young and adult mice. OP-1 is expressed in kidney; however, OP-2 and BMP-2 mRNAs were not detected in any organs studied, suggesting an early developmental role.

Murine osteogenic protein (OP-1): high levels of mRNA in kidney

The murine OP-1 gene (EMBL accession No. X56906) encoding the homolog of human osteogenic protein-1 was isolated from cDNA and genomic libraries using human OP-1 cDNA as probe. The deduced murine OP-1 amino acid sequence revealed 11 amino acids changes, three of them in the mature protein. Murine OP-1 probes were used for analysis of OP-1 mRNA in mouse embryo and organ tissues. Northern blot hybridization revealed multiple mRNA species: the major species of 2.2 kb, minor species of 1.8 and 2.4 kb and a large 4 kb species, which may represent alternative splices. Tissue specific expression was studied in brain, lung, heart, liver, spleen, kidney, adrenal and bladder tissue. Maximal levels of OP-1 mRNA were found in kidney which may explain the phenomenon of epithelial osteogenesis, first described by Huggins in 1931 using epithelium from the urinary tract. Moreover, our data suggest that kidneys may be the main site of OP-1 synthesis, even though it is distant from its physiological site of action, skeletal bone.

Bovine osteogenic protein is composed of dimers of OP-1 and BMP-2A, two members of the transforming growth factor-beta superfamily

A bone-inductive protein has been purified from bovine bone and designated as osteogenic protein (OP). The purified OP induces new bone at less than 5 ng with half-maximal bone differentiation activity at about 20 ng/25 mg of matrix implant in a subcutaneous bone induction assay. The purified osteogenic protein is composed of disulfide-linked dimers that migrate on sodium dodecyl sulfate gels as a diffuse band with an apparent molecular weight of 30,000. Upon reduction, the dimers yield two subunits that migrate with molecular weights of 18,000 and 16,000. Both subunits are glycosylated. After chemical or enzymatic deglycosylation, the dimers migrate as a diffuse 27-kDa band that upon reduction yields two polypeptides that migrate at 16 kDa and 14 kDa, respectively. The carbohydrate moiety does not appear to be essential for biological activity since the deglycosylated proteins are capable of inducing bone formation in vivo. Amino acid sequences of peptides generated by proteolytic digestion show that the subunits are distinct but related members of the transforming growth factor-beta super-family. The 18-kDa subunit is the protein product of the bovine equivalent of the human OP-1 gene and the 16-kDa subunit is the protein product of the bovine equivalent of the human BMP-2A gene.

OP-1 cDNA encodes an osteogenic protein in the TGF-beta family

Amino acid sequences of two tryptic peptides derived from enriched bovine osteogenic protein preparations revealed considerable homology to two members of the TGF-beta (transforming growth factor beta) supergene family, DPP (decapentaplegic protein) of Drosophila and Vg-1 (vegetal protein) of Xenopus. Building upon this information we constructed a synthetic consensus gene to use as a probe to screen human genomic libraries. This resulted in the isolation of three interrelated genes. Among these were BMP-2b and BMP-3 which have recently been described by others. The third gene, termed OP-1 (osteogenic protein one), is new and was subsequently shown to encode the human homolog of a major component of bovine osteogenic protein. The genomic clones were used to isolate the corresponding complementary DNA (cDNA) clones. Sequence analysis indicates that OP-1 is a relative of the murine Vgr-1 (Vg-1 related gene). This report describes the cDNA structure and putative amino acid sequence of OP-1.

The yeast ubiquitin genes: a family of natural gene fusions

Ubiquitin is a 76-residue protein highly conserved among eukaryotes. Conjugation of ubiquitin to intracellular proteins mediates their selective degradation in vivo. We describe a family of four ubiquitin-coding loci in the yeast Saccharomyces cerevisiae. UB11, UB12 and UB13 encode hybrid proteins in which ubiquitin is fused to unrelated ('tail') amino acid sequences. The ubiquitin coding elements of UB11 and UB12 are interrupted at identical positions by non-homologous introns. UB11 and UB12 encode identical 52-residue tails, whereas UB13 encodes a different 76-residue tail. The tail amino acid sequences are highly conserved between yeast and mammals. Each tail contains a putative metal-binding, nucleic acid-binding domain of the form Cys-X2-4-Cys-X2-15-Cys-X2-4-Cys, suggesting that these proteins may function by binding to DNA. The fourth gene, UB14, encodes a polyubiquitin precursor protein containing five ubiquitin repeats in a head-to-tail, spacerless arrangement. All four ubiquitin genes are expressed in exponentially growing cells, while in stationary-phase cells the expression of UB11 and UB12 is repressed. The UB14 gene, which is strongly inducible by starvation, high temperatures and other stresses, contains in its upstream region strong homologies to the consensus 'heat shock box' nucleotide sequence. Elsewhere we show that the essential function of the UB14 gene is to provide ubiquitin to cells under stress.

The yeast polyubiquitin gene is essential for resistance to high temperatures, starvation, and other stresses

Conjugation of ubiquitin to intracellular proteins mediates their selective degradation in eukaryotes. In the yeast Saccharomyces cerevisiae, four distinct ubiquitin-coding loci have been described. UBI1, UBI2, and UBI3 each encode hybrid proteins in which ubiquitin is fused to unrelated sequences. The fourth gene, UBI4, contains five ubiquitin-coding elements in a head-to-tail arrangement, and thus encodes a polyubiquitin precursor protein. A precise, oligonucleotide-directed deletion of UBI4 was constructed in vitro and substituted in the yeast genome in place of the wild-type allele. ubi4 deletion mutants are viable as vegetative cells, grow at wild-type rates, and contain wild-type levels of free ubiquitin under exponential growth conditions. However, although ubi4/UBI4 diploids can form four initially viable spores, the two ubi4 spores within the ascus lose viability extremely rapidly, apparently a novel phenotype in yeast. Furthermore, ubi4/ubi4 diploids are sporulation-defective. ubi4 mutants are also hypersensitive to high temperatures, starvation, and amino acid analogs. These three conditions, while diverse in nature, are all known to induce stress proteins. Expression of the UBI4 gene is similarly induced by either heat stress or starvation. These results indicate that UBI4 is specifically required for the resistance of cells to stress, and that ubiquitin is an essential component of the stress response system.

The yeast ubiquitin gene: head-to-tail repeats encoding a polyubiquitin precursor protein

Ubiquitin, a 76-residue protein, occurs in cells either free or covalently joined to a variety of protein species, from chromosomal histones to cytoplasmic proteins. Conjugation of ubiquitin to proteolytic substrates is essential for the selective degradation of intracellular proteins in higher eukaryotes. We show here that a protein homologous to human ubiquitin exists in the yeast Saccharomyces cerevisiae, and that yeast extracts conjugate human ubiquitin to a variety of endogenous proteins in an ATP-dependent reaction. We have isolated the S. cerevisiae ubiquitin gene and found it to contain six consecutive ubiquitin-coding repeats in a found it to contain six consecutive ubiquitin-coding repeats in a head-to-tail arrangement. This apparently unique gene organization suggests that yeast ubiquitin is generated by processing of a precursor protein in which several exact repeats of the ubiquitin amino acid sequence are joined directly via Gly-Met peptide bonds between the last and first residues of mature ubiquitin, respectively. Ubiquitin-coding yeast DNA repeats are restricted to a single genomic locus; although the sequenced repeats differ in up to 27 of 228 bases per repeat, they encode identical amino acid sequences. As this predicted amino acid sequence differs in only 3 of 76 residues from that of ubiquitin in higher eukaryotes, ubiquitin is apparently the most conserved of known proteins.

Isolation of protein uH2A using a one step preparative gel electrophoresis

A one step electrophoretic procedure for the isolation of protein uH2A has been devised which may improve the overall yield. The improvement involves elimination of intermediate steps which might result in the decrease of the yield. The method may serve as an alternate to the conventional methods and can also be used successfully for the isolation of several different proteins.