Inactive Pseudogene Research Articles

Long-read sequencing: An effective method for genetic analysis of CYP21A2 variation in congenital adrenal hyperplasia

BackgroundThe sequence similarity between CYP21A2 gene and its inactive pseudogene CYP21A1P, and copy number variation (CNV) caused by unequal crossover, make it challenging to characterize the CYP21A2 gene through traditional methods. This study aimed to evaluate the clinical utility of the long-read sequencing (LRS) method in carrier screening and genetic diagnosis of congenital adrenal hyperplasia (CAH) by comparing the efficiency of the LRS method with the conventional multiplex ligation-dependent probe amplification (MLPA) plus Sanger sequencing approaches in CYP21A2 analysis. MethodsIn a retrospective study, full sequence analysis of the CYP21A2 and CYP21A1P was performed for three pedigrees through long-range locus-specific PCR followed by LRS based on the Pacific Biosciences (PacBio, California, USA) single-molecule real-time (SMRT) platform, and the results were compared with those obtained from next-generation sequencing (NGS)-based whole exome sequencing (WES) and the traditional methods of MLPA plus Sanger sequencing. ResultsThe LRS method successfully identified seven CYP21A2 variants, including three single nucleotide variants (NM_000500.9:c.1451G > C p.(Arg484Pro), c.293-13A/C > G (IVS2-13A/C > G), c.518 T > A p.(Ile173Asn)), one 111-bp polynucleotide insertion, one set of 3′URT variants (NM_000500.9:c.*368 T > C, c.*390A > G, c.*440C > T, c.*443 T > C) and two types of chimeric genes and straightforwardly depicted the inheritance patterns of these variants within families. Moreover, the LRS method enabled us to determine the cis–trans configuration of multiple variants in one assay, without the need to analyze additional family samples. Compared with traditional methods, this LRS method can achieve a precise, comprehensive and intuitive result in the genetic diagnosis of 21-hydroxylase deficiency (21-OHD). ConclusionThe LRS method is comprehensive in CYP21A2 analysis and intuitive in result presentation, which holds substantial promise in clinical application as a crucial tool for carrier screening and genetic diagnosis of CAH.

Unexpectedly high mutation rate of cyp11b1 compared to cyp21a2 in randomly-selected turkish women: a large screening study.

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders resulting from enzyme deficiencies associated with steroidogenesis. The clinical presentation of non-classic CAH (NCAH) in females is often indistinguishable from other hyperandrogenic disorders like polycystic ovary syndrome (PCOS). The data on the prevalence of NCAH in unselected women in the literature is scanty. The research aimed to evaluate the prevalence of NCAH, carrier frequencies, and the correlation between clinical symptoms and genotype in Turkish women. The study group comprised two hundred and seventy randomly-selected unrelated asymptomatic women of reproductive age (18-45). Subjects were recruited from female blood donors. All volunteers underwent clinical examination and hormone measurements. The protein-encoding exons and exon-intron boundaries of the CYP21A2, CYP11B1, HSD3β2 and CYP21A2 promoter were sequenced by direct DNA sequencing. After genotyping, seven (2.2%) individuals were diagnosed with NCAH. The heterozygous carrier frequencies of CYP21A2, CYP21A2 promoter, CYP11B1, and HSD3β2 genes with 34, 34, 41, and 1 pathologic mutation were determined at 12.6%, 12.6%, 15.2%, and 0.37% of volunteers, respectively. Gene-conversion (GC) frequencies between CYP21A2/CYP21A1P and CYP11B1/CYP11B2 were determined as 10.4% and 14.8%, respectively. Despite GC-derived higher mutation frequency determined in the CYP11B1 gene, the reason for the low frequency of NCAH due to 11OHD compared to 21OHD might be that gene-conversion arises with active CYP11B2 rather than an inactive pseudogene. HSD3β1 exhibits high homology with HSD3β2 located on the same chromosome; remarkably, it demonstrates low heterozygosity and no GC, most probably the outcome of a tissue-specific expression pattern.

Pervasive Suicidal Integrases in Deep-Sea Archaea

Mobile genetic elements (MGEs) often encode integrases which catalyze the site-specific insertion of their genetic information into the host genome and the reverse reaction of excision. Hyperthermophilic archaea harbor integrases belonging to the SSV-family which carry the MGE recombination site within their open reading frame. Upon integration into the host genome, SSV integrases disrupt their own gene into two inactive pseudogenes and are termed suicidal for this reason. The evolutionary maintenance of suicidal integrases, concurring with the high prevalence and multiples recruitments of these recombinases by archaeal MGEs, is highly paradoxical. To elucidate this phenomenon, we analyzed the wide phylogenomic distribution of a prominent class of suicidal integrases which revealed a highly variable integration site specificity. Our results highlighted the remarkable hybrid nature of these enzymes encoded from the assembly of inactive pseudogenes of different origins. The characterization of the biological properties of one of these integrases, IntpT26-2 showed that this enzyme was active over a wide range of temperatures up to 99 °C and displayed a less-stringent site specificity requirement than comparable integrases. These observations concurred in explaining the pervasiveness of these suicidal integrases in the most hyperthermophilic organisms. The biochemical and phylogenomic data presented here revealed a target site switching system operating on highly thermostable integrases and suggested a new model for split gene reconstitution. By generating fast-evolving pseudogenes at high frequency, suicidal integrases constitute a powerful model to approach the molecular mechanisms involved in the generation of active genes variants by the recombination of proto-genes.

Joint Genomic and Proteomic Analysis Identifies Meta-Trait Characteristics of Virulent and Non-virulent Staphylococcus aureus Strains.

Staphylococcus aureus is an opportunistic pathogen of humans and warm-blooded animals and presents a growing threat in terms of multi-drug resistance. Despite numerous studies, the basis of staphylococcal virulence and switching between commensal and pathogenic phenotypes is not fully understood. Using genomics, we show here that S. aureus strains exhibiting virulent (VIR) and non-virulent (NVIR) phenotypes in a chicken embryo infection model genetically fall into two separate groups, with the VIR group being much more cohesive than the NVIR group. Significantly, the genes encoding known staphylococcal virulence factors, such as clumping factors, are either found in different allelic variants in the genomes of NVIR strains (compared to VIR strains) or are inactive pseudogenes. Moreover, the pyruvate carboxylase and gamma-aminobutyrate permease genes, which were previously linked with virulence, are pseudogenized in NVIR strain ch22. Further, we use comprehensive proteomics tools to characterize strains that show opposing phenotypes in a chicken embryo virulence model. VIR strain CH21 had an elevated level of diapolycopene oxygenase involved in staphyloxanthin production (protection against free radicals) and expressed a higher level of immunoglobulin-binding protein Sbi on its surface compared to NVIR strain ch22. Furthermore, joint genomic and proteomic approaches linked the elevated production of superoxide dismutase and DNA-binding protein by NVIR strain ch22 with gene duplications.

CASPASE-12 is not a protective factor for rheumatoid arthritis in African-Americans (P4106)

Abstract CASPASE-12 (CASP12) modulates inflammation due to its ability to down-regulate inflammatory cytokines, particularly interleukin-1. Most humans possess the inactive pseudogene allele (CASP12p1) but a functional, non-truncated CASP12 allele [single nucleotide polymorphism #rs497116; A->G; ter124R] is found in 20% of persons of African descent. CASP12 is a risk factor for sepsis in persons of African descent. Rheumatoid arthritis (RA) is a serious and complex autoimmune disease that involves significant joint inflammation and destruction, and interleukin-1 contributes to the pathogenesis of RA. To determine if CASP12 may be protective against RA due to its anti-inflammatory functions, we genotyped 742 patients with rheumatoid arthritis and 342 controls from the Consortium for Longitudinal Evaluation of African-Americans with Early Rheumatoid Arthritis and the Veterans Affairs Rheumatoid Arthritis registries. Of RA patients, 17 (2.29%) were homozygous for CASP12, 146 (19.7%) were heterozygous, and 579 (78%) were homozygous for CASP12p1. These numbers did not vary significantly from controls. No significant differences were observed for CASP12 genotype on age of disease onset, seropositivity for rheumatoid factor or anti-CCP, baseline joint erosion, joint space narrowing scores, overall disease scores, C-reactive protein levels or erythrocyte sedimentation rates. Thus, CASP12 does not protect against RA in African-American patients, nor mitigates disease parameters.

Functional characterization and evolution of the isotuberculosinol operon in Mycobacterium tuberculosis and related Mycobacteria

Terpenoid metabolites are important to the cellular function, structural integrity, and pathogenesis of the human-specific pathogen Mycobacterium tuberculosis (Mtb). Genetic and biochemical investigations have indicated a role for the diterpenoid isotuberculosinol (isoTb) early in the infection process. There are only two genes (Rv3377c and Rv3378c) required for production of isoTb, yet these are found in what appears to be a five-gene terpenoid/isoprenoid biosynthetic operon. Of the three remaining genes (Rv3379c, Rv3382c, and Rv3383c), previous work has indicated that Rv3379c is an inactive pseudo-gene. Here we demonstrate that Rv3382c and Rv3383c encode biochemically redundant machinery for isoprenoid metabolism, encoding a functional 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (LytB) for isoprenoid precursor production and a geranylgeranyl diphosphate (GGPP) synthase, respectively, for which the Mtb genome contains other functional isozymes (Rv1110 and Rv0562, respectively). These results complete the characterization of the isoTb biosynthetic operon, as well as further elucidating isoprenoid metabolism in Mtb. In addition, we have investigated the evolutionary origin of this operon, revealing Mtb-specific conservation of the diterpene synthase genes responsible for isoTb biosynthesis, which supports our previously advanced hypothesis that isoTb acts as a human-specific pathogenic metabolite and is consistent with the human host specificity of Mtb. Intriguingly, our results revealed that many mycobacteria contain orthologs for both Rv3383c and Rv0562, suggesting a potentially important role for these functionally redundant GGPP synthases in the evolution of terpenoid/isoprenoid metabolism in the mycobacteria.

The Arthrobacter Species FB24 Arth_1007 (DnaB) Intein Is a Pseudogene

An Arthrobacter species FB24 gene (locus tag Arth_1007) was previously annotated as a putative intein-containing DnaB helicase of phage origin (Arsp-FB24 DnaB intein). However, it is not a helicase gene because the sequence similarity is limited to inteins. In fact, the flanking exteins total only 66 amino acids. Therefore, the intein should be referred to as the Arsp-FB24 Arth_1007 intein. The Arsp-FB24 Arth_1007 intein failed to splice in its native precursor and in a model precursor. We previously noted that the Arsp-FB24 Arth_1007 intein is the only putative Class 3 intein that is missing the catalytically essential Cys at position 4 of intein Motif F, which is one of the three defining signature residues of this class. Additionally, a catalytically essential His in position 10 of intein Motif B is also absent; this His is the most conserved residue amongst all inteins. Splicing activity was not rescued when these two catalytically important positions were ‘reverted’ back to their consensus residues. This study restores the unity of the Class 3 intein signature sequence in active inteins by demonstrating that the Arsp-FB24 Arth_1007 intein is an inactive pseudogene.

P.H282N and p.Y191H: 2 novel CYP21A2 mutations in Italian congenital adrenal hyperplasia patients

More than 90% of all cases of congenital adrenal hyperplasia (CAH) result from steroid 21-hydroxylase gene (CYP21A2) mutations. The CYP21A2 gene is located in the human leukocyte antigen (HLA) class III region on the short arm of chromosome 6p21.3, along with an inactive pseudogene, CYP21A1P, that is 98% homologous in its coding sequence with CYP21A2. Most CYP21A2 mutations result from intergenic recombinations between CYP21A2 and the closely linked CYP21A1P pseudogene. Rare mutations not generated by gene conversion account for only 5% to 10% of 21-hydroxylase deficiency alleles. However, detection of these rare and spontaneous mutations has continued to expand worldwide. We identified 2 novel CYP21A2 missense mutations (p.H282N and p.Y191H) in 2 Italian patients with simple-virilizing and nonclassic CAH forms. Functional analysis of these CYP21A2 mutations was performed. Functional in vitro assay for mutagenized CYP21A2 enzymes was performed in transiently transfected mammalian cells to test the residual enzyme activity and the apparent kinetic values. The residual activities obtained allowed us to classify the p.H282N and p.Y191H variants as simple-virilizing and nonclassic CAH associated mutations, respectively. These results correlate with the rate of severity of the patients' disease. This finding provides a further contribution for assisting in the diagnosis of CAH patients.

Chimeric CYP21A1P/ CYP21A2 genes identified in Czech patients with congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) comprises a group of autosomal recessive disorders caused by an enzymatic deficiency which impairs the biosynthesis of cortisol and, in the majority of severe cases, also the biosynthesis of aldosterone. Approximately 95% of all CAH cases are caused by mutations in the steroid 21-hydroxylase gene ( CYP21A2). The CYP21A2 gene and its inactive pseudogene ( CYP21A1P) are located within the HLA class III region of the major histocompatibility complex (MHC) locus on chromosome 6p21.3. In this study, we describe chimeric CYP21A1P/ CYP21A2 genes detected in our patients with 21-hydroxylase deficiency (21OHD). Chimeric CYP21A1P/ CYP21A2 genes were present in 171 out of 508 mutated CYP21A2 alleles (33.8%). We detected four types of chimeric CYP21A1P/ CYP21A2 genes: three of them have been described previously as CH-1, CH-3, CH-4, and one type is novel. The novel chimeric gene, termed CH-7, was detected in 21.4% of the mutant alleles. Possible causes of CYP21A1P/ CYP21A2 formation are associated with 1) high recombination rate in the MHC locus, 2) high recombination rate between highly homologous genes and pseudogenes in the CYP21 gene area, and 3) the existence of chi-like sequences and repetitive minisatellite consensus sequences in CYP21A2 and CYP21A1P which play a role in promoting genetic recombination.

Molecular diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency: an update of new CYP21A2 mutations

Steroid 21-hydroxylase deficiency is present in more than 90% of patients with congenital adrenal hyperplasia, an inherited metabolic disorder of adrenal steroidogenesis. Impaired enzymatic activity leads to the accumulation of metabolic intermediates (progesterone and 17-hydroxyprogesterone), which results in excessive androgen production and varied signs of virilisation. CYP21A2 is an active gene and encodes for the steroid 21-hydroxylase enzyme, whereas CYP21A1P is an inactive pseudogene that contains a series of deleterious mutations. The major part of disease-causing mutations in CYP21A2 alleles are CYP21A1P-derived sequence transferred to the active gene by macro or microconversion events. Approximately 5% of all disease-causing CYP21A2 alleles harbour rare mutations that do not originate from the pseudogene. A list of all reported CYP21A2 mutations can be found in the CYP21A2 database created by the Human Cytochrome P450 (CYP) Allele Nomenclature Committee (http:www.imm.Ki.se/CYPalleles/cyp21.htm). Unfortunately, the last update of this database was in 2006. However, over the last 4 years many other novel CYP21A2 mutations have been reported in PubMed. The aim of this review is to provide a focus on the molecular and genetic aspects of the diagnosis of 21-hydroxylase deficiency. In addition, an updated list of the last new CYP21A2 mutations is included.

Down-regulation of PROS1 Gene Expression by 17β-Estradiol via Estrogen Receptor α (ERα)-Sp1 Interaction Recruiting Receptor-interacting Protein 140 and the Corepressor-HDAC3 Complex

Pregnant women show a low level of protein S (PS) in plasma, which is known to be a risk for deep venous thrombosis. 17Beta-estradiol (E(2)), an estrogen that increases in concentration in the late stages of pregnancy, regulates the expression of various genes via the estrogen receptor (ER). Here, we investigated the molecular mechanisms behind the reduction in PS levels caused by E(2) in HepG2-ERalpha cells, which stably express ERalpha, and also the genomic ER signaling pathway, which modulates the ligand-dependent repression of the PSalpha gene (PROS1). We observed that E(2) repressed the production of mRNA and antigen of PS. A luciferase reporter assay revealed that E(2) down-regulated PROS1 promoter activity and that this E(2)-dependent repression disappeared upon the deletion or mutation of two adjacent GC-rich motifs in the promoter. An electrophoretic mobility shift assay and DNA pulldown assay revealed that the GC-rich motifs were associated with Sp1, Sp3, and ERalpha. In a chromatin immunoprecipitation assay, we found ERalpha-Sp protein-promoter interaction involved in the E(2)-dependent repression of PROS1 transcription. Furthermore, we demonstrated that E(2) treatment recruited RIP140 and the NCoR-SMRT-HDAC3 complex to the PROS1 promoter, which hypoacetylated chromatin. Taken together, this suggested that E(2) might repress PROS1 transcription depending upon ERalpha-Sp1 recruiting transcriptional repressors in HepG2-ERalpha cells and, consequently, that high levels of E(2) leading to reduced levels of plasma PS would be a risk for deep venous thrombosis in pregnant women.

Sequence Polymorphisms Provide a Common Consensus Sequence for GPR41 and GPR42

GPR41 and GPR42 are two closely related genes that are part of a cluster of four adjacent G protein-coupled receptors (GPCRs) (GPR40, 41, 42, and 43) localized on human chromosome 19. There are only six nucleotide and amino acid differences between GPR41 and GPR42. High sequence homology between these two genes suggests that they are the result of a recent duplication event. Mutagenesis studies have previously shown that amino acid 174 is important for functional signaling since conversion of R174 (found in GPR41) to W174 (found in GPR42) silences the response to short chain fatty acids, raising the possibility that GPR42 might be an inactive pseudogene. In the present study, we present evidence showing that the six amino acid differences, including that R/W174 are polymorphisms rather than gene-specific differences between GPR41 and GPR42. Most importantly, of the 202 GPR42 alleles that were genotyped, 123 (61%) had arginine at amino acid 174, suggesting that GPR42 could potentially be a functional gene in a significant fraction of the human population and should therefore not be categorically characterized as an inactive pseudogene. In addition, a second copy of GPR40 was found to localize between GPR41 and GPR42 genes in human and chimp, suggesting that the duplication event that generated GPR42 in human and chimp might have involved a 12.5 kb DNA fragment that also contains GPR40. This second copy of the GPR40 gene is a pseudogene since it has diverged extensively from GPR40 and does not contain an open reading frame.

Alpha-fetoprotein related gene ( ARG): A new member of the albumin gene family that is no longer functional in primates

The serum albumin gene family is comprised of albumin, alpha-fetoprotein, alpha-albumin ( afamin), and the more distantly related Vitamin D binding protein. These genes arose from a common ancestor through a series of duplication events, are expressed primarily in the liver and tightly linked in all species where this has been investigated. Here, we describe a fifth member of the albumin gene family that we have named Alpha-fetoprotein Related Gene ( ARG) since it exhibits greatest similarity to this family member. ARG is activated in the liver perinatally, but is expressed at very low levels. The ARG gene is present and intact in the mouse, rat, dog and horse genomes. In contrast, the ARG gene in human, chimpanzee, rhesus monkey, and marmoset contains a number of mutations common to all four species, indicating that this gene has been an inactive pseudogene in primates for at least 40 million years. Low expression and aberrant splicing of the ARG gene in the mouse liver suggests that ARG may have less functional significance than other members of the serum albumin gene family even in species where it is still intact.

Two novel CYP21A2 missense mutations in Italian patients with 21‐hydroxylase deficiency: Identification and functional characterisation

Steroid 21-hydroxylase deficiency is present in more than 90% of patients with congenital adrenal hyperplasia (CAH), an inherited metabolic disorder of adrenal steroidogenesis. Impaired enzymatic activity leads to the accumulation of metabolic intermediates (progesterone and 17-hydroxyprogesterone), which results in excessive androgen production and varied signs of virilisation. CYP21A2 is an active gene and encodes for the steroid 21-hydroxylase enzyme, whereas CYP21A1P is an inactive pseudogene that contains a series of deleterious mutations. The major part of disease- causing mutations in CYP21A2 alleles are CYP21A1P-derived sequence transferred to the active gene by macro or microconversion events. Only around 5% of all disease-causing CYP21A2 alleles harbour rare mutations that do not originate from the pseudogene. In this report, we report the characterisation of two novel CYP21A2 missense mutations (p.H119R and p.I194N) found in two unrelated Italian patients with nonclassic (NC) CAH clinical diagnosis. Functional in vitro assays for mutagenized CYP21 enzymes were performed in transiently transfected mammalian cells to test the residual enzyme activity and the apparent kinetic values. The residual activities obtained for p.H119R and p.I194N mutants allowed to classify them as NC-CAH associated mutations. These results correlate with the rate of severity of the patients' disease. Finally, the new p.H119R and p.I194N mutations should be included in the panel of those already listed for association with the NC form of 21-hydroxylase deficiency.

A new CYP21A2 nonsense mutation causing severe 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused primarily by defects in the steroid 21-hydroxylase gene (CYP21A2). The CYP21A2 gene is located in the HLA class III region on the short arm of chromosome 6p21.3, along with an inactive pseudogene, CYP21A1P, that is 98% homologous with CYP21A2 in its coding sequence. Most mutations found in the CYP21A2 gene are normally present in the pseudogene, implying that recombination events (microconversion) between these two genes may lead to the transfer of mutations from the pseudogene to the functional gene. Approximately only 5% of all CYP21A2 alleles causing disease harbour rare mutations not originating from the pseudogene. However, detection of these rare and spontaneous mutations has continued to expand worldwide. In this report, we describe the clinical and genetic findings in a Romanian newborn suffering from classic salt wasting form of CAH due to severe 21-hydroxylase deficiency.

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In this issue

The Evolution of Seminal Ribonuclease: Pseudogene Reactivation or Multiple Gene Inactivation Events?

Two approaches, one novel, are applied to analyze the divergent evolution of ruminant seminal ribonucleases (RNases), paralogs of the well-known pancreatic RNases of mammals. Here, the goal was to identify periods of divergence of seminal RNase under functional constraints, periods of divergence as a pseudogene, and periods of divergence driven by positive selection pressures. The classical approach involves the analysis of nonsynonymous to synonymous replacements ratios (omega) for the branches of the seminal RNase evolutionary tree. The novel approach coupled these analyses with the mapping of substitutions on the folded structure of the protein. These analyses suggest that seminal RNase diverged during much of its history after divergence from pancreatic RNase as a functioning protein, followed by homoplastic inactivations to create pseudogenes in multiple ruminant lineages. Further, they are consistent with adaptive evolution only in the most recent episode leading to the gene in modern oxen. These conclusions contrast sharply with the view, cited widely in the literature, that seminal RNase decayed after its formation by gene duplication into an inactive pseudogene, whose lesions were repaired in a reactivation event. Further, the 2 approaches, omega estimation and mapping of replacements on the protein structure, were compared by examining their utility for establishing the functional status of the seminal RNase genes in 2 deer species. Hog and roe deer share common lesions, which strongly suggests that the gene was inactive in their last common ancestor. In this specific example, the crystallographic approach made the correct implication more strongly than the omega approach. Studies of this type should contribute to an integrated framework of tools to assign functional and nonfunctional episodes to recently created gene duplicates and to understand more broadly how gene duplication leads to the emergence of proteins with novel functions.

A Novel 13-bp Deletion in Exon 1 of CYP21 Gene Causing Severe Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) is a common autosomal recessive disorder mainly caused by defects in the steroid 21-hydroxylase gene (CYP21). In most cases, this defect is the result of gene conversion events between the functional CYP21 gene and the adjacent inactive pseudogene (CYP21P). Previous screening for mutations of 21-hydroxylase gene in 51 unrelated Tunisian CAH patients revealed 4 novel mutations that have not been reported to occur in the CYP21P pseudogene. The present paper describes the fifth new small 13-bp deletion in exon 1 found after sequencing the CYP21 gene of a Tunisian patient suffering from the salt-wasting form of CAH. The patient is a girl born to consanguineous parents; she is homozygous for a novel deletion. The 13-bp deletion causes a stop codon at amino acid 47, which is likely to result in an enzyme with no activity. Both parents are heterozygous for the small deletion as confirmed by nested PCR method. This novel mutation has not been reported to occur in the CYP21P pseudogene, indicating a casual mutagenic event rather than a conversion one.

Biochemical Characterization of Phosphoryl Transfer Involving HPr of the Phosphoenolpyruvate-Dependent Phosphotransferase System in Treponema denticola, an Organism that Lacks PTS Permeases

Treponema pallidum and Treponema denticola encode within their genomes homologues of energy coupling and regulatory proteins of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) but no recognizable homologues of PTS permeases. These homologues include (1) Enzyme I, (2) HPr, (3) two IIA(Ntr)-like proteins, and (4) HPr(Ser) kinase/phosphorylase (HprK). Because the Enzyme I-encoding gene in T. pallidum is an inactive pseudogene and because all other pts genes in both T. pallidum and T. denticola are actively expressed, the primary sensory transduction mechanism for signal detection and transmission appears to involve HprK rather than EI. We have overexpressed and purified to near homogeneity four of the five PTS proteins from T. denticola. Purified HprK phosphorylates HPr with ATP, probably on serine, while Enzyme I phosphorylates HPr with PEP, probably on histidine. Furthermore, HPr(His)-P can transfer its phosphoryl group to IIA(Ntr)-1. Factors and conditions regulating phosphoryl transfer prove to differ from those described previously for Bacillus subtilis, but cross-enzymatic activities between the Treponema, Salmonella, and Bacillus phosphoryl-transfer systems could be demonstrated. Kinetic analyses revealed that the allosterically regulated HPr kinase/phosphorylase differs from its homologues in Bacillus subtilis and other low G+C Gram-positive bacteria in being primed for kinase activity rather than phosphorylase activity in the absence of allosteric effectors. The characteristics of this enzyme and the Treponema phosphoryl-transfer chain imply unique modes of signal detection and sensory transmission. This paper provides the first biochemical description of PTS phosphoryl-transfer chains in an organism that lacks PTS permeases.

Spermine Synthesis Is Required for Normal Viability, Growth, and Fertility in the Mouse

Spermidine is essential for viability in eukaryotes but the importance of the longer polyamine spermine has not been established. Spermine is formed from spermidine by the action of spermine synthase, an aminopropyltransferase, whose gene (SpmS) is located on the X chromosome. Deletion of part of the X chromosome that include SpmS in Gy mice leads to a striking phenotype in affected males that includes altered phosphate metabolism and symptoms of hypophosphatemic rickets, circling behavior, hyperactivity, head shaking, inner ear abnormalities, deafness, sterility, a profound postnatal growth retardation, and a propensity to sudden death. It was not clear to what extent these alterations were due to the loss of spermine synthase activity, since this chromosomal deletion extends well beyond the SpmS gene and includes at least one other gene termed Phex. We have bred the Gy carrier female mice with transgenic mice (CAG/SpmS mice) that express spermine synthase from the ubiquitous CAG promoter. The resulting Gy-CAG/SpmS mice had extremely high levels of spermine synthase and contained spermine in all tissues examined. These mice had a normal life span and fertility and a normal growth rate except for a reduction in body weight due to a loss of bone mass that was consistent with the observation that the derangement in phosphate metabolism is due to the loss of the Phex gene and was not restored. These results show that spermine synthesis is needed for normal growth, viability, and fertility in male mice and that regulation of spermine synthase content is not required.