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Distribution of IGFBP-rP1 in normal human tissues.

IGFBP-rP1/mac25 is a recently described member of the insulin-like growth factor binding protein (IGFBP) family. It has structural homology to the other members of the IGFBP family but has a lower affinity for insulin-like growth factors (IGFs). In previous studies using RNA blot hybridization, it was shown that the expression of IGFBP-rP1/mac25 was ubiquitous in normal human tissues. In this report we show by immunohistochemistry that the expression of IGFBP-rP1/mac25 is actually restricted to certain organs and specific cell types. We used an antibody raised against a decapeptide of the C-terminal part of the protein that recognizes a approximately 37-kD protein under reduced conditions. The immunohistochemistry performed on normal human tissues showed a ubiquitous intense staining of peripheral nerves and a variable degree of positive staining in smooth muscle cells, including those from blood vessel walls, gut, bladder, and prostate. Cilia from the respiratory system, epididymis, and fallopian tube showed intense immunoreactivity. Most endothelial cells showed some positivity, whereas fat cells, plasma cells, and lymphocytes were negative. There was specific expression limited to certain cell types in the kidney, adrenal gland, and skeletal muscle, indicating a possible specialized function of IGFBP-rP1/mac25 in these organs. We further noted an opposite pattern of staining in the lining epithelium of breast (typically positive) and prostate glands (largely negative). The specific localization of IGFBP-rP1/mac25 as described implies a function of the protein. However, its regulation within the IGF axis or a possible direct action of IGFBP-rP1/mac25 remains to be demonstrated.

Antibodies↗

Three novel and the common Arg677Ter RP1 protein truncating mutations causing autosomal dominant retinitis pigmentosa in a Spanish population.

BACKGROUND: Retinitis pigmentosa (RP), a clinically and genetically heterogeneous group of retinal degeneration disorders affecting the photoreceptor cells, is one of the leading causes of genetic blindness. Mutations in the photoreceptor-specific gene RP1 account for 3-10% of cases of autosomal dominant RP (adRP). Most of these mutations are clustered in a 500 bp region of exon 4 of RP1. METHODS: Denaturing gradient gel electrophoresis (DGGE) analysis and direct genomic sequencing were used to evaluate the 5' coding region of exon 4 of the RP1 gene for mutations in 150 unrelated index adRP patients. Ophthalmic and electrophysiological examination of RP patients and relatives according to pre-existing protocols were carried out. RESULTS: Three novel disease-causing mutations in RP1 were detected: Q686X, K705fsX712 and K722fsX737, predicting truncated proteins. One novel missense mutation, Thr752Met, was detected in one family but the mutation does not co-segregate in the family, thereby excluding this amino acid variation in the protein as a cause of the disease. We found the Arg677Ter mutation, previously reported in other populations, in two independent families, confirming that this mutation is also present in a Spanish population. CONCLUSION: Most of the mutations reported in the RP1 gene associated with adRP are expected to encode mutant truncated proteins that are approximately one third or half of the size of wild type protein. Patients with mutations in RP1 showed mild RP with variability in phenotype severity. We also observed several cases of non-penetrant mutations.

Amino Acid Sequence↗

Allelic and haplotypic diversity at the rp1 rust resistance locus of maize.

The maize Rp1 rust resistance locus is a complex consisting of a family of closely related resistance genes. The number of Rp1 paralogs in different maize lines (haplotypes) varied from a single gene in some stocks of the inbred A188 to >50 genes in haplotypes carrying the Rp1-A and Rp1-H specificities. The sequences of paralogs in unrelated haplotypes differ, indicating that the genetic diversity of Rp1-related genes is extremely broad in maize. Two unrelated haplotypes with five or nine paralogs had identical resistance phenotypes (Rp1-D) encoded in genes that differed by three nucleotides resulting in a single amino acid substitution. Genes in some haplotypes are more similar to each other than to any of the genes in other haplotypes indicating that they are evolving in a concerted fashion.

Base Sequence↗

[Structural instability of co-integrates formed during interaction of plasmid R57 with pB322 and RP1. Possible role of IS1 element in the degradation of co-integrates].

The conjugative plasmid R57 determines resistance to ampicillin and chloramphenicol. Earlier it was shown that R57 encodes site-specific recA-independent recombinase, which acts in cis and resolves IS1-mediated cointegrates arising in the Escherichia coli recA cells between R57 and pBR322. In the present work the properties of the cointegrates between R57 and pBR322 or RP1 arising in the E. coli rec+ strains were studied. It was found that the cointegrates between R57 and pBR322, obtained by mating of the respective biplasmid donors of E. coli rec+ and the rec+ recipients, lost as a result of deletion a large DNA segment of R57 containing determinant Cmr. The resulting hybrid replicons preserved determinants Apr and Tcr of pBR322 and the R57 conjugative properties and were structurally identical. By using plasmid RP1ts12, which is temperature-sensitive in replication, it was demonstrated that in cells rec+ the cointegrates between R57 and RP1 are extremely unstable. On storage they undergo structural degradation mainly affecting the RP1 replicon. The degradation products of the hydrid complex had lost their RP1 genes but preserved the R57 functional determinants. For elucidation of the observed phenomena the properties of the IS1-mediated cointegrates between pBR322:Tn9 and plasmid pBR3.1--deletion derivative of RP1 were studied. It was found that insertion of IS1 sometimes resulted in formation of unstable cointegrates capable of resolving and loosing determinant Cmr with a high frequency. It was suggested that IS1 encodes the site-specific recombinase responsible for resolution of the IS1-mediated cointegrates and deletion generation. Expression of this recombinase appears to be dependent on structure of the insertion sites. The possible role of IS1 and recombinase encoded by it in resolution and structural instability of the cointegrates between R57 and pBR322 or RP1 is discussed.

Chromosome Mapping↗

[Thermosensitive vector derived from RP1 plasmid for detection of transposable elements].

The involvement of the transposable DNA element of E. coli K12 chromosome in integrative recombination of RP1 plasmid was studied. Using temperature sensitive for replication plasmid RP1ts12--the derivative of RP1 which contains mutated transposon Tnl, it was shown that integration of RP1 into host chromosome and Hfr formation may occur according to a mechanism mediated by chromosome IS-elements. Plasmids that are desintegrated from the chromosome of these Hfrs contain discrete DNA segments (IS-elements) and possess elevated frequency of integration into chromosome of rec+ cells. The latter was used for selection of RP1ts12 recombinants carrying chromosome IS. For identification of IS involved in RP1 integration the number of independent RP1ts 12 recombinants was subjected to restriction and heteroduplex analysis. By analysing recombinants integrated into bacterial chromosome with frequency 5 X 10(-3), a new IS-element of E. coli K12 designated IS111 was discovered. IS111-element is about 1500bp of length, contains Smal, Pst1 and BamH1 restriction endonuclease sites and was found in the same position on the plasmid RP1 in two different orientations. IS-elements that have been revealed in a number of other RP1ts12 recombinants were preliminary identified as IS1-like elements. One recombinants plasmid was found to have an IS5-like elements. The activity of IS-elements inserted into RP1ts12 in recA-dependent integrative recombination was estimated. From the data of absolute and relative RP1ts12 integration frequencies mediated by IS111, IS1- and IS5-like elements a conclusion was made about the absence of E. coli K12 chromosome IS-elements in RP1 plasmid. The Hfr-formation and chromosomal gene transfer by recombinant plasmids RP1ts12: IS111 were studied. The possibility to use insertion RP1ts12 derivatives for the estimation of copies number, mapping and definition of orientation of IS-elements in bacterial chromosome and the possibilities for detection of transposable DNA elements using RP1ts12 in a wide range of gram-negative bacteria are discussed.

Bacterial Proteins↗

[Integration of plasmid RP1 with the chromosome of Escherichia coli K-12 recA. 2 classes of Hfr strains].

Integration of broad host range RP1 plasmid into the chromosome of Escherichia coli K-12 recA- cells has been studied. Using temperature-sensitive for replication plasmids pVD1 and pVD3, the derivatives of RP1, it has been shown that integration of RP1 into the bacterial chromosome results in formation of two classes of Hfr strains. Properties of these Hfrs have been examined. From the data obtained, it has been concluded that the plasmid integration and formation of one of the Hfrs classes appear to be mediated by transposon Tn1 residing on RP1. The other class of Hfr strains is formed due to a stable integration of RP1. In the course of analysis of R+ transconjugants arising at low frequency in crosses between stable Hfrs and E. coli rec+ recipients, it has been found that the significant part of them contain plasmid-chromosome hybrids (R-prim plasmids). On the basis of the latter results, a new simple method for R' plasmids selection has been proposed. Using restriction endonuclease analysis, the structure of plasmids that were excised from chromosomes of the stable Hfr strains and were comparable in their size to RP1, has been investigated. Probable mechanisms of the stable Hfr strains formation are discussed.

Chromosomes, Bacterial↗

RP1 in Chinese: Eight novel variants and evidence that truncation of the extreme C-terminal does not cause retinitis pigmentosa.

Heterozygous truncating mutations in the RP1 gene cause approximately 7% of autosomal dominant retinitis pigmentosa (RP) cases. To examine the role of RP1 mutations in RP, we screened 101 unrelated Chinese RP patients (unselected for mode of inheritance) and 190 elderly normal control subjects for sequence changes in the coding exons for the 2156 amino acid RP1 protein. One patient had a mutation, thus RP1 mutations cause about 0.0% to 5.4% (95% confidence interval) of all RP among Chinese. The mutation was R677X, the most common found in Americans. Five other known sequence changes were found. In addition, nine novel sequence alterations were identified: 746G>A (R249H), 1437G>T (M479I), 2116G>C (G706R), 3024G>A (Q1008Q), 3188G>A (Q1063R), 5797C>T (R1933X), 6423A>G (I2141M), and the variants 6542C>T and 6676T>A, both in the 3' untranslated region. One control subject and three members of a non-RP family were heterozygous for R1933X, which is therefore likely to be a non-disease-causing variant. The most C-terminal truncation previously reported was due to Tyr1053 (1-bp del) and occurred in RP patients. Thus the presence of a normal level of at least part of RP1 between amino acids 1052 and 1933 appears necessary to prevent RP. Hum Mutat 17:436, 2001.

3' Untranslated Regions↗

Reversion of an ilvB mutation in Pseudomonas aeruginosa in the presence of a derivative of RP1 plasmid.

We have isolated a derivative of RP1, a broad-host-range plasmid, in whose presence the ilvB112 mutation of Pseudomonas aeruginosa strain PU21 reverts at a high frequency. This derivative of RP1 (RP1-ilvB+ complex) may have arisen by a fusion of the P. aeruginosa ilvB gene with RP1 during their co-transfer into strain PU21. The RP1 derivative is not very stable in the PU21 background but it can apparently be stabilized by its integration into the host chromosome, resulting in an Hfr-type donor strain, SP500.

Mutation↗

Aberrant mRNA processing of the maize Rp1-D rust resistance gene in wheat and barley.

The maize Rp1-D gene confers race-specific resistance against Puccinia sorghi (common leaf rust) isolates containing a corresponding avrRp1-D avirulence gene. An Rp1-D genomic clone and a similar Rp1-D transgene regulated by the maize ubiquitin promoter were transformed independently into susceptible maize lines and shown to confer Rp1-D resistance, demonstrating that this resistance can be transferred as a single gene. Transfer of these functional transgenes into wheat and barley did not result in novel resistances when these plants were challenged with isolates of wheat stem rust (P. graminis), wheat leaf rust (P. triticina), or barley leaf rust (P. hordei). Regardless of the promoter employed, low levels of gene expression were observed. When constitutive promoters were used for transgene expression, a majority of Rp1-D transcripts were truncated in the nucleotide binding site-encoding region by premature polyadenylation. This aberrant mRNA processing was unrelated to gene function because an inactive version of the gene also generated such transcripts. These data demonstrate that resistance gene transfer between species may not be limited only by divergence of signaling effector molecules and pathogen avirulence ligands, but potentially also by more fundamental gene expression and transcript processing limitations.

Carrier Proteins↗

Plasmid RP1-mediated susceptibility of Acinetobacter calcoaceticus to rat polymorphonuclear leukocyte granule contents.

The resistance plasmid RP1 was transferred by conjugation to a plasmidless strain of Acinetobacter calcoaceticus. Acquisition and expression of RP1 by A. calcoaceticus HO1-N was associated with an increase in sensitivity to the antimicrobial activity of extracted contents from rat polymorphonuclear leukocyte granules. Plasmid RP1-associated antibiotic resistance and sensitivity to granule contents were cured by exposure to acridine orange. Assays with granule extract fractions separated by fast protein liquid chromatography showed myeloperoxidase, protease, and lysozyme fractions to possess little or no antimicrobial activity against the A. calcoaceticus strains. A protein fraction designated peak D, containing two low-molecular-weight cationic peptides (M. J. Loeffelholz and M. C. Modrzakowski, Anal. Biochem., in press), did possess antimicrobial activity against both HO1-N and Ho1-N(RP1) strains, with the HO1-N(RP1) strain being significantly more sensitive.

Acinetobacter↗

Novel variants in the hotspot region of RP1 in South African patients with retinitis pigmentosa.

PURPOSE: Mutations in the hotspot of RP1 are reportedly responsible for 4-7% of autosomal dominant retinitis pigmentosa (ADRP) in the United States, Canada, and Europe. South Africa (SA) has unique subpopulations and a comparatively low observed frequency of rhodopsin mutations, which lead to this investigation of the contribution of RP1 mutations to the ADRP disease burden in SA. METHODS: Fifty-seven affected, unrelated South African individuals with ADRP were selected for mutation screening of the RP1 hotspot, using denaturing high performance liquid chromatography (HPLC). Variants were identified by direct sequencing, after which cosegregation analysis and population frequency studies were performed using restriction fragment length polymorphism analysis, nondenaturing HPLC, or denaturing HPLC. RESULTS: Three mutations were identified, including two novel sequence variations and the common Arg677X mutation. A wide spectrum of disease severity was observed in the families with these RP1 gene mutations. Two nondisease-associated polymorphisms were also detected, with the frequency of one of these variants being significantly low in Black African individuals. CONCLUSIONS: Mutations were only found in Caucasian families with origins in the British Isles. The observed RP1 mutation frequency of 5.3% in SA ADRP patients is comparable to the frequency reported in other populations.

Eye Proteins↗

RP1, a new member of the adenomatous polyposis coli-binding EB1-like gene family, is differentially expressed in activated T cells.

Cross-linking of the CD3 and CD28 molecules on T lymphocytes represents one of the most effective signals for T lymphocyte activation and triggering of their cytotoxic effector function. To identify genes that are expressed in T cells after stimulation, mRNA from T lymphocytes that had been activated by the simultaneous stimulation of the CD3 and CD28 trigger molecules was transcribed for a differential mRNA display analysis into cDNA and was compared with cDNA from CD28- or CD3-activated or resting lymphocytes. Differential expression was confirmed subsequently by Northern blot analysis. One of the cDNA fragments expressed specifically in CD3- and CD28-activated T cells was designated RP1. The predictive protein-coding region of RP1 had a significant homology to members of the recently found adenomatous polyposis coli (APC) protein-binding EB1 gene family, which codes for yet unknown protein(s). Bacterially expressed RP1 protein revealed specific binding to wild-type but not to mutated APC protein. The rapid up-regulation of RP1 mRNA in properly activated T cells suggests that this gene might belong to the immediate/early gene family, which controls the signal transduction cascade downstream of the TCR. As the expression level of the RP1 gene in activated T cells and a spectrum of tumor-derived cell lines correlates with the proliferative status of the cells, members of the EB1-like gene family may not only be involved in the tumorigenesis of colorectal cancers but may also play a role in the proliferative control of normal cells.

Adenomatous Polyposis Coli↗

Exome sequencing identifies a homozygous splice site variant in RP1 as the underlying cause of autosomal recessive retinitis pigmentosa in a Pakistani family.

BACKGROUND: Mutations in RP1 gene are the third leading cause of inherited retinal dystrophies (IRDs) in Pakistani families. PATIENTS: A two-generation consanguineous Pakistani family underwent both clinical and genetic analyses. Clinical examinations included visual acuity test, visual field, fundoscopy, and ocular coherence tomography (OCT). Whole exome sequencing (WES) was performed on the proband's DNA, and Sanger sequencing was performed to validate the WES findings. Splicing prediction tools such as Human Splicing Finder (HSF), NNSplice predictor, SpliceAI, MaxENTScan, and SpliceRover were used. RESULTS: A nuclear family of seven children, comprising five affected individuals (four males and one female) and two healthy siblings, was recruited from northwestern Pakistan. The proband was a 49-years old male who was presented with complaints of decreased visual acuity and night blindness since early childhood. Upon clinical evaluation, the proband appeared to have severely reduced visual acuity of hand movement (HM), bilateral visual field constriction, a waxy pale disc with vascular attenuation, pigmentary bone spicules at the periphery associated with chorioretinal degeneration, diffuse macular atrophy, and horizontal nystagmus in both of his eyes. Exome sequencing (ES) in the proband identified a homozygous splice site variant (NM_006269.2: c.615 + 1G > A) in RP1 gene. In-silico analysis, genotype-phenotype co-segregation study, and literature survey strongly supported the causality of the detected variant. CONCLUSIONS: We report a previously known pathogenic splice site variant of RP1 as the underlying cause of early-onset autosomal recessive retinitis pigmentosa (arRP) in a Pakistani family. We contemplate that the detected allele might constitute a mutational hotspot in RP1.

Humans↗

Four ubiquitously expressed genes, RD (D6S45)-SKI2W (SKIV2L)-DOM3Z-RP1 (D6S60E), are present between complement component genes factor B and C4 in the class III region of the HLA.

The association of the HLA class III region with many diseases motivates the investigation of unidentified genes in the 30-kb segment between complement component genes Bf and C4. RD, which codes for a putative RNA binding protein, is 205 bp downstream of Bf. SKI2W (HGMW-approved symbol SKIV2L), a DEVH-box gene probably involved in RNA turnover, is 171 bp downstream of RD (HGMW-approved symbol D6S45). RP1 (HGMW-approved symbol D6S60E) is located 611 bp upstream of C4. The DNA sequence between human RD and RP1 was determined and the exon-intron structure of SKI2W elucidated. SKI2W consists of 28 exons. The putative RNA helicase domain of Ski2w is encoded by 9 exons. Further analysis of the 2.5-kb intergenic sequence between SKI2W and RP1 led to the discovery of DOM3Z. The full-length cDNA sequence of DOM3Z encodes 396 amino acids with a leucine zipper motif. Dom3z-related proteins are present in simple and complex eukaryotes. In Caenorhabditis elegans, Dom3z-related protein could be involved in the development of germ cells. Human RD-SKI2W and DOM3Z-RP1 are arranged as two head-to-head oriented gene pairs with unmethylated CpG sequences at the common 5' regulatory region of each gene pair. The ubiquitous expression pattern suggests that these four genes are probably housekeeping genes.

Amino Acid Sequence↗

Isolation of an Hfr donor of Pseudomonas aeruginosa PAO by insertion of the plasmid RP1 into the tryptophan synthase gene.

A derivative of the IncP-1 plasmid RP1, temperature-sensitive for maintenance, was inserted into the Pseudomonas aeruginosa chromosome by selection for a plasmid marker (carbenicillin resistance) at non-permissive temperature. In one strain, PAO 1000, the plasmid was stably integrated in the trpA, B gene cluster mapped at 27 min, as shown by the following evidence. (i) Trp+ transductants lost all plasmid markers. (ii) Cleared lysates of PAO 1000 showed no plasmid band typical of the autonomous RP1 in agarose gel electrophoresis. (iii) No transfer of carbenicillin resistance by PAO 1000 was detectable. (iv) PAO 1000 mobilised the chromosome from an origin at, or very near, the plasmid insertion site with high frequency (recovery of proximal markers greater than or equal to 10(-3) per donor). Matings on the plate with and without interruption of conjugation showed that chromosome transfer was unidirectional. (v) Recombinants from PAO 1000-mediated crosses did not inherit plasmid markers or the trpA, B mutation. A derivative of PAO 1000 was obtained which had lost the Hfr property and all plasmid markers except carbenicillin resistance. This strain (PAO 1001), when carrying the autonomous RP1 plasmid, was capable of unidirectional chromosome mobilisation like PAO 1000, but with 50-fold lower efficiency. We propose that integration of the temperature-sensitive RP1 plasmid in PAO 1000 occurred via transposition of Tn1, the element specifying carbenicillin resistance.

Conjugation, Genetic↗

Linkage mapping of autosomal dominant retinitis pigmentosa (RP1) to the pericentric region of human chromosome 8.

Linkage mapping in a large, seven-generation family with type 2 autosomal dominant retinitis pigmentosa (ADRP) demonstrates linkage between the disease locus (RP1) and DNA markers on the short arm of human chromosome 8. Five markers were most informative for mapping ADRP in this family using two-point linkage analysis. The markers, their maximum lod scores, and recombination distances were ANK1 (ankyrin)--2.0 at 16%; D8S5 (TL11)--5.3 at 17%; D8S87 [a(CA)n repeat]--7.2 at 14%; LPL (lipoprotein lipase)--1.5 at 26%; and PLAT (plasminigen activator, tissue)--10.6 at 7%. Multipoint linkage analysis, using a simplified pedigree structure for the family (which contains 192 individuals and two inbreeding loops), gave a maximum lod score of 12.2 for RP1 at a distance 8.1 cM proximal to PLAT in the pericentric region of the chromosome. Based on linkage data from the CEPH (Paris) reference families and physical mapping information from a somatic cell hybrid panel of chromosome 8 fragments, the most likely order for four of these five loci and the diseases locus is 8pter-LPL-D8S5-D8S87-PLAT-RP1. (The precise location of ANK1 relative to PLAT in this map is not established). The most likely location for RP1 is in the pericentric region of the chromosome. Recently, several families with ADRP with tight linkage to the rhodopsin locus at 3q21-q24 were reported and a number of specific rhodopsin mutations in families with ADRP have since been reported. In other ADRP families, including the one in this study, linkage to rhodopsin has been excluded. Thus mutations at two different loci, at least, have been shown to cause ADRP. There is no remarkable clinical disparity in the expression of disease caused by these different loci.

Base Sequence↗

Chromosomal localization and promoter analysis of the adenomatous polyposis coli binding protein RP1.

The EB1/RP1 family is a new protein family that is characterized by the ability of its members to serve as interacting partners for the adenomatous polyposis coli (APC) tumour suppressor protein and tubulin. Data obtained with highly conserved yeast homologues suggest that the EB1/RP1 protein family promotes cytoplasmic microtubule dynamics and contributes to the sensor mechanism controlling the cytokinesis checkpoint during mitosis. However, the precise function of this protein family in mammalian cells has not been elucidated so far and remains unclear. Here, we report on the genomic localization of the RP1 gene and the characterization of the corresponding promoter. The RP1 gene was found to be encoded on chromosome 18q21, a locus which is altered or deleted in up to 50% of all patients with colorectal cancer. Promoter analysis revealed that the RP1 gene is under the control of a strong promoter that was 10 times more active in mammalian cells when compared to SV40 promoter. Members of the cyclic AMP response element binding protein family (CREB1 and CREB2) could be identified as transcription factors binding specifically within the RP1 promoter sequence.

Base Sequence↗

New rust resistance specificities associated with recombination in the Rp1 complex in maize.

We address the question of whether genetic reassortment events, including unequal crossing over and gene conversion, at the Rp1 complex are capable of generating novel resistance specificities that were not present in the parents. Some 176 events involving genetic reassortment within the Rp1 complex were screened for novel resistance specificities with a set of 11 different rust biotypes. Most (150/176) of the events were susceptible to all tested rust biotypes, providing no evidence for new specificities. Eleven events selected as double-resistant recombinants, when screened with the 11 test biotypes, showed the combined resistance of the two parental types consistent with a simple recombination and pyramiding of the parental resistances. Nine events selected either as having partial resistance or complete susceptibility to a single biotype possessed resistance to a subset of the biotypes that the parents were resistant to, suggesting segregation of resistance genes present in the parental Rp1 complex. Four events gave rise to novel specificities being resistant to at least one rust biotype to which both parents were susceptible. All four had flanking marker exchange, demonstrating that crossing over within the Rp1 complex is associated with the appearance of new rust resistance specificities.

Basidiomycota↗