Human Homologous Proteins Research Articles

Identification of Peptidoglycan Glycosyltransferase FtsI as a Potential Drug Target against Salmonella Enteritidis and Salmonella Typhimurium Serovars Through Subtractive Genomics, Molecular Docking and Molecular Dynamics Simulation Approaches.

Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium are among the main causative agents of nontyphoidal Salmonella infections, imposing a significant global health burden. The emergence of antibiotic resistance in these pathogens underscores the need for innovative therapeutic strategies. To identify proteins as potential drug targets against Salmonella Enteritidis and Salmonella Typhimurium serovars using In silico approaches. In this study, a subtractive genomics approach was employed to identify potential drug targets. The whole proteome of Salmonella enteritidis PT4 and Salmonella typhimurium (D23580), containing 393 and 478 proteins, respectively, was analyzed through subtractive genomics to identify human homologous proteins of the pathogen and also the proteins linked to shared metabolic pathways of pathogen and its host. Subsequent analysis revealed 19 common essential proteins shared by both strains. To ensure hostspecificity, we identified 10 non-homologous proteins absent in humans. Among these proteins, peptidoglycan glycosyltransferase FtsI was pivotal, participating in pathogen-specific pathways and making it a promising drug target. Molecular docking highlighted two potential compounds, Balsamenonon A and 3,3',4',7-Tetrahydroxyflavylium, with strong binding affinities with FtsI. A 100 ns molecular dynamics simulation having 10,000 frames substantiated the strong binding affinity and demonstrated the enduring stability of the predicted compounds at the docked site. The findings in this study provide the foundation for drug development strategies against Salmonella infections, which can contribute to the prospective development of natural and cost-effective drugs targeting Salmonella Enteritidis and Salmonella Typhimurium.

L(1)10Bb serves as a conservative determinant for soma-germline communications via cellular non-autonomous effects within the testicular stem cell niche

The testicular stem cell niche is the central regulator of spermatogenesis in Drosophila melanogaster. However, the underlying regulatory mechanisms are unclear. This study demonstrated the crucial role of lethal (1) 10Bb [l(1)10Bb] in regulating the testicular stem cell niche. Dysfunction of l(1)10Bb in early-stage cyst cells led to male fertility disorders and compromised cyst stem cell maintenance. Moreover, the dysfunction of l(1)10Bb in early-stage cyst cells exerted non-autonomous effects on germline stem cell differentiation, independently of hub signals. Notably, our study highlights the rescue of testicular defects through ectopic expression of L(1)10Bb and the human homologous protein BUD31 homolog (BUD31). In addition, l(1)10Bb dysfunction in early-stage cyst cells downregulated the expression of spliceosome subunits in the Sm and the precursor RNA processing complexes. Collectively, our findings established l(1)10Bb as a pivotal factor in the modulation of Drosophila soma-germline communications within the testicular stem cell niche.

Overexpression of watermelon m6A methyltransferase ClMTB enhances drought tolerance in tobacco by mitigating oxidative stress and photosynthesis inhibition and modulating stress-responsive gene expression

N6-methyladenosine (m6A) in RNA is a very important post-transcriptional modification mechanism in eukaryotes. It has been reported to have important regulatory roles in some stress responses in model plants, but there has been no research regarding m6A modifications in watermelon. In this study, we cloned and characterized m6A methyltransferase, ClMTB (mRNA adenosine methylase B, METTL14 human homolog protein) in watermelon. ClMTB expression could be weakly induced by drought stress as determined by the quantitative real-time PCR (qRT-PCR) and Promoter::GUS analyses. ClMTB over-expressed in tobacco plants increased drought tolerance via enhancing reactive oxygen species (ROS) scavenging system and alleviating photosynthesis inhibition under drought. Transcriptome profiles indicated the multiple hormone and stress-responsive genes were specifically induced in over-expressed ClMTB plants under drought conditions. These results suggest that ClMTB-mediated m6A modification serves as a positive regulatory factor of drought tolerance. This study is the first one to provide an understanding of the specific roles of ClMTB in watermelon adaptation to drought stress, and may also provide important insights into the signaling pathway mediated by m6A modification in response to stress conditions.

N-Glycosylation Enhances Conformational Flexibility of Protein Disulfide Isomerase Revealed by Microsecond Molecular Dynamics and Markov State Modeling.

Secreted proteins of eukaryotes are decorated with branched carbohydrate oligomers called glycans. This fact is only starting to be considered for in silico investigations of protein dynamics. Using all-atom molecular dynamics (MD) simulations and Markov state modeling (MSM), we unveil the influence of glycans on the conformational flexibility of the multidomain protein disulfide isomerase (PDI), which is a ubiquitous chaperone in the endoplasmic reticulum (ER). Yeast PDI (yPDI) from Saccharomyces cerevisiae is glycosylated at asparagine side chains and the knowledge of its five modified sites enables a realistic computational modeling. We compare simulations of glycosylated and unglycosylated yPDI and find that the presence of glycan-glycan and glycan-protein interactions influences the flexibility of PDI in different ways. For example, glycosylation reduces interdomain interactions, shifting the conformational ensemble toward more open, extended structures. In addition, we compare our results on yPDI with structural information of homologous proteins such as human PDI (hPDI), which is natively unglycosylated. Interestingly, hPDI lacks a surface recess that is present in yPDI. We find that glycosylation of yPDI facilitates its catalytic site to reach close to this surface recess. Hence, this might point to a possible functional relevance of glycosylation in yeast to act on substrates, while glycosylation seems redundant for the human homologous protein. We conclude that glycosylation is fundamental for protein dynamics, making it a necessity for a truthful representation of the flexibility and function in in silico studies of glycoproteins.

Proteome Analysis of Urinary Biomarkers in Acute Hypercoagulable State Rat Model.

Thrombotic diseases are usually preceded by a hypercoagulable state in the body. This study aimed to screen potential urinary biomarkers for hypercoagulable state based on proteome analysis. Wistar rats were administered with the hemostatic agent etamsylate to establish hypercoagulable state. Urine samples were collected for proteome analysis. We found 20 proteins with levels more than 1.5-fold in difference between control rats and model rats. We searched human homologs of 20 rat proteins and identified 13 human proteins. Of the 13 human homologous proteins, nine were members of human core urinary proteome. Human homologous proteins of differential proteins were highly expressed in 31 human tissues, especially in the kidneys followed by digestive system and reproductive system. Surprisingly, we did not identify known coagulation factors as differential proteins in the urine of model rats. Hypercoagulable state of the body may not involve direct changes in coagulation factors but causes the changes upstream of the coagulation cascade system. Common differential urinary proteins between different hypercoagulable states suggest some common pathways in the formation of hypercoagulable states and may serve as potential biomarkers for the prevention and treatment of thrombotic diseases.

Integrative multiomics analysis of Premolis semirufa caterpillar venom in the search for molecules leading to a joint disease

The joint disease called pararamosis is an occupational disease caused by accidental contact with bristles of the caterpillar Premolis semirufa. The chronic inflammatory process narrows the joint space and causes alterations in bone structure and cartilage degeneration, leading to joint stiffness. Aiming to determine the bristle components that could be responsible for this peculiar envenomation, in this work we have examined the toxin composition of the caterpillar bristles extract and compared it with the differentially expressed genes (DEGs) in synovial biopsies of patients affected with rheumatoid arthritis (RA) and osteoarthritis (OA). Among the proteins identified, 129 presented an average of 63% homology with human proteins and shared important conserved domains. Among the human homologous proteins, we identified seven DEGs upregulated in synovial biopsies from RA or OA patients using meta-analysis. This approach allowed us to suggest possible toxins from the pararama bristles that could be responsible for starting the joint disease observed in pararamosis. Moreover, the study of pararamosis, in turn, may lead to the discovery of specific pharmacological targets related to the early stages of articular diseases.

The clinical impact of cross-reactions between allergens on allergic skin diseases.

The route of allergen sensing via the skin appears to influence the immune system towards mounting a type 2 response, especially in genetically predisposed individuals. Allergens recognized this way may derive from microbial, animal, food, or other plant sources and trigger atopic dermatitis. Allergens can be grouped into families depending on their structure and function, harboring significant structural and sequence similarities. Cross-reactivity between allergens is believed to arise as a consequence, and to underlie the development of further atopic diseases. Especially for the plant allergens of the families of PR10-related proteins and profilins, immune cross-reactions have been described. Actual studies support that food and pollen allergens can aggravate skin lesions in patients suffering from atopic dermatitis. Further on, allergens derived from air-borne or skin-borne fungi belong to common allergen families and bear cross-reactivity potential. Cross-reactivity to human homologous proteins, so-called autoallergens, is discussed to contribute to the chronification of atopic dermatitis. Due to high evolutionary conservation, allergic reactions can be triggered by highly homologous members of allergen families on the humoral as well as on the cellular level.

Subtractive genomics approach towards the identification of novel therapeutic targets against human Bartonella bacilliformis

Abstract Bartonella bacilliformis, a causative agent of Bartonellosis or Carrion's disease, has become resistant to antibacterial agents. To suggest effective novel drug targets, a comprehensive in silico subtractive genomic approach was employed in the genome of B. bacilliformis subsp. ver097. Different bioinformatics tools and online servers were utilized to determine human homologous proteins of the pathogen, as well as proteins associated with common metabolic pathways of pathogen and host. Only seven proteins were associated in pathogen specific pathways, which were further screened to determine drug or vaccine targeted membrane proteins. ‘ABC transporter permease’ and ‘Flagellar biosynthesis protein FlhA’ were found to be novel drug targets which showed the highest level of antigenicity. Moreover, ‘Flagellar biosynthesis protein FlhA’ exhibited broad spectrum conservancy with other Bartonella bacilliformis strains. Consequently, it might be used for development of novel drugs and therapeutic components for the successful treatment of infections caused by Bartonella bacilliformis.

Potential Drug Target Identification of Legionella pneumophila by Subtractive Genome Analysis: An In Silico Approach

Though Legionella pneumophila is an opportunistic pathogen, recent reports about multi drug resistance in L. pneumophila is alarming. Annotated whole genome provides a pool of information which is applied for therapeutic drug targets identification in pathogenic bacteria. Subtractive genomic analysis is a pragmatic approach to screen the essential proteins present in pathogen but absent in host. Phylogenetically closely related L. pneumophila str. Philadelphia and L. pneumophila str. ATCC43209 protein profiles were analyzed to identify putative drug targets. Paralogous duplicate profiles were primarily discarded using CD-hit suit. Six hundred and ninety one L. pneumophila str. Philadelphia and 690 L. pneumophila str. ATCC43209 human homologous proteins were excluded using blstP. Among the human non-homologous proteins, the essential proteins for bacteria were separated using DEG tool. For both strains, one hundred and nineteen essential proteins were marked which participate in various metabolic pathways. Among them 11 unique proteins were found. Beside it, 15 and 16 exposed surface proteins were present in strain Philadelphia and ATCC43209 respectively. These unique and cell surface proteins can be utilized for effective drug and vaccine targets.
 Bangladesh J Microbiol, Volume 35 Number 2 December 2018, pp 102-107

Pathway based therapeutic targets identification and development of an interactive database CampyNIBase of Campylobacter jejuni RM1221 through non-redundant protein dataset.

The bacterial species Campylobacter jejuni RM1221 (CjR) is the primary cause of campylobacteriosis which poses a global threat for human health. Over the years the efficacy of antibiotic treatment is becoming more fruitless due to the development of multiple drug resistant strains. Therefore, identification of new drug targets is a valuable tool for the development of new treatments for affected patients and can be obtained by targeting essential protein(s) of CjR. We conducted this in silico study in order to identify therapeutic targets by subtractive CjR proteome analysis. The most important proteins of the CjR proteome, which includes chokepoint enzymes, plasmid, virulence and antibiotic resistant proteins were annotated and subjected to subtractive analyses to filter out the CjR essential proteins from duplicate or human homologous proteins. Through the subtractive and characterization analysis we have identified 38 eligible therapeutic targets including 1 potential vaccine target. Also, 12 potential targets were found in interactive network, 5 targets to be dealt with FDA approved drugs and one pathway as potential pathway based drug target. In addition, a comprehensive database ‘CampyNIBase’ has also been developed. Besides the results of this study, the database is enriched with other information such as 3D models of the identified targets, experimental structures and Expressed Sequence Tag (EST) sequences. This study, including the database might be exploited for future research and the identification of effective therapeutics against campylobacteriosis. URL: (http://nib.portal.gov.bd/site/page/4516e965-8935-4129-8c3f-df95e754c562#Banner).

Expression and function of NKp46 W32R: the human homologous protein of mouse NKp46 W32R (No\xe9)

Natural killer (NK) cells eradicate infected cells and tumors following the triggering of activating receptors, like the Natural Cytotoxicity Receptors (NCRs), which include NKp30, NKp44 and NKp46. NKp46 is the only NCR expressed in mice (mNKp46), and except for some Innate Lymphoid Cell (ILC) populations (ILC1/3 subsets), its expression is restricted to NK cells. Previously, a mouse named Noé was generated in which a random point mutation (W32R) impaired the cell surface expression of mNKp46. Interestingly, the Noé mice NK cells expressed twice as much of the transcription factor Helios, and displayed general non-NKp46 specific hyperactivity. We recently showed that the mNKp46 W32R (Noé) protein was expressed on the surface of various cells; albeit slowly and unstably, that it is aberrantly glycosylated and accumulates in the ER. Interestingly, the Tryptophan (Trp) residue in position 32 is conserved between humans and mice. Therefore, we studied here the human orthologue protein of mNKp46 W32R, the human NKp46 W32R. We demonstrated that NKp46 W32R is aberrantly glycosylated, accumulates in the ER, and is unstable on the cell surface. Furthermore, we showed that overexpression of NKp46 W32R or Helios resulted in augmented NK cell activation, which may be applied to boost NK activity for therapeutic applications.

Identification of potential apicoplast associated therapeutic targets in human and animal pathogen Toxoplasma gondii ME49.

Toxoplasma gondii ME49 is an obligatory intracellular apicomplexa parasite that causes toxoplasmosis in humans, domesticated and wild animals. Waterborne outbreaks of acute toxoplasmosis worldwide reinforce the transmission of Toxoplasma gondii ME49 to humans through contaminated water and may have a greater epidemiological impact than previously believed. In the quest for drug and vaccine target identification subtractive genomics involving subtraction between the host and pathogen genome has been implemented for enlisting essential pathogen specific proteins. Using this approach, our analysis on both human and Toxoplasma gondii ME49 reveals that out of 7987 protein coding sequences of the pathogen, 950 represent essential non human-homologous proteins. Subcellular localization prediction & comparative-biochemical pathway analysis of these essential proteins gives a list of apicoplast-associated proteins having unique pathogen-specific metabolic pathway. These apicoplast-associated enzymes involved in fatty acid biosynthesis pathway of Toxoplasma gondii ME49, may be used as potential drug targets, as the pathway is vital for the protozoan's survival. Structure prediction of drug target proteins was done using fold based recognition method. Screening of the functional inhibitors against these novel targets may result in discovery of novel therapeutic compounds that can be effective against Toxoplasma gondii ME49. DEG - Database of Essential Gene, KEGG - Kyoto Encyclopaedia of Genes and Genomes, KAAS - KEGG Automated Annotation Server, PFP - Protein Function Prediction, COG - Cluster of Orthologous Genes.

PUTATIVE DRUG TARGET IDENTIFICATION FOR CHLAMYDIA TRACHOMATIS: AN INSILICO PROTEOME ANALYSIS

The whole genome sequences of pathogenic bacteria and the host genome such as human has provided a Subtractive genomic approach, which can be used to identify potent vaccine and drug targets. In the present study subtractive genomic approach has been used to identify therapeutic target in Chlamydia trachomatis . C.trachomatis infection is now the most common sexually transmitted disease worldwide. The BlastP search against Homo sapiens revealed 551 non-homologous protein sequences out of 874 in C.trachomati . Further analysis of these non human homologous proteins predicted that 142 essential proteins were involved in unique metabolic pathways of C.trachomatis . The prediction of sub-cellular localization of the essential proteins was used to identify the membrane proteins which can be used as vaccine targets. There are 63 unique essential non-human homologous therapeutic targets found in the current study, which plays a vital role in the Peptidoglycan biosynthesis, Phosphotransferase system, Fatty acid biosynthesis and Bacterial secretion system of C.trachomatis .

Crystal Structure of Mycobacterium tuberculosis Zinc-dependent Metalloprotease-1 (Zmp1), a Metalloprotease Involved in Pathogenicity

Mycobacterium tuberculosis, the causative agent of tuberculosis, parasitizes host macrophages. The resistance of the tubercle bacilli to the macrophage hostile environment relates to their ability to impair phagosome maturation and its fusion with the lysosome, thus preventing the formation of the phago-lysosome and eventually arresting the process of phagocytosis. The M. tuberculosis zinc-dependent metalloprotease Zmp1 has been proposed to play a key role in the process of phagosome maturation inhibition and emerged as an important player in pathogenesis. Here, we report the crystal structure of wild-type Zmp1 at 2.6 Å resolution in complex with the generic zinc metalloprotease inhibitor phosphoramidon, which we demonstrated to inhibit the enzyme potently. Our data represent the first structural characterization of a bacterial member of the zinc-dependent M13 endopeptidase family and revealed a significant degree of conservation with eukaryotic enzymes. However, structural comparison of the Zmp1-phosphoramidon complex with homologous human proteins neprilysin and endothelin-converting enzyme-1 revealed unique features of the Zmp1 active site to be exploited for the rational design of specific inhibitors that may prove useful as a pharmacological tool for better understanding Zmp1 biological function.

Efficient separation of homologous α-lactalbumin from transgenic bovine milk using optimized hydrophobic interaction chromatography

Transgenic bovine milk could be a rich source of recombinant human proteins. However, the co-presence of bovine and human homologous proteins can be a challenge for product purification. In this study, the average surface hydrophobicity and electric potential of human α-lactalbumin (HLA) and bovine α-lactalbumin (BLA) were analyzed and compared through the exposure area calculation of different amino acids. Based on the analysis, calcium independent hydrophobic interaction chromatography was selected for separation of recombinant human α-lactalbumin (rHLA) from BLA in transgenic bovine milk. The operating conditions for the best separation of two proteins were predicted by fluorescence data. Three commercially available HIC resins (Butyl Sepharose 4 FF, Octyl Sepharose 4 FF, Phenyl Sepharose 6 FF) were compared. The transgenic milk was skimmed and treated by pH adjustment to remove a large quantity of casein protein. The supernatant was loaded on the hydrophobic interaction chromatographic matrix. The correct elution fraction was further treated with gel filtration chromatography. The overall recovery of rHLA was up to 67.1% with the purity greater than 95%. Circular dichroism spectroscopy (CD) and mass spectrogram (MS) confirmed the native state and glycosylated form of the purified rHLA.

Immunological mechanism underlying the immune response to recombinant human protein therapeutics

Recombinant human (rhu) protein therapeutics are powerful tools to treat several severe diseases such as multiple sclerosis and diabetes mellitus, among others. A major drawback of these proteins is the production of anti-drug antibodies (ADAs). In some cases, these ADAs have neutralizing capacity and can interfere with the efficacy and safety of the drug. Little is known about the immunological mechanisms underlying the unwanted immune response against human homolog protein therapeutics. This article aims to provide current insights into recent immunological developments and to link this with regard to production of ADAs. A particular focus is given to aggregates being present in a rhu protein formulation and their impact on the immune system, subsequently leading to breakage of tolerance and formation of ADAs. Aggregation is one of the key factors in immunogenicity and by reducing aggregation one can reduce immunogenicity and make drugs safer and more efficient.

Induction of Neutrophil Gelatinase-Associated Lipocalin in Vascular Injury via Activation of Nuclear Factor-κB

Neutrophil gelatinase-associated lipocalin (NGAL) has recently emerged as an important modulator of cell homeostasis. Elevated plasma NGAL levels, possibly because of activation of blood leukocytes, are associated with atherosclerosis. However, little is known about induction of NGAL expression in blood vessels. Using a rat carotid artery injury model, we found that NGAL was highly induced in the intima after angioplasty but was attenuated by adenovirus-mediated expression of a dominant-negative mutant of inhibitor of nuclear factor (NF)-kappaB kinase beta (dnIKKbeta). Expression of NGAL mRNA and protein was also up-regulated in an NF-kappaB-dependent manner in rat and human vascular smooth muscle cells (SMCs) in response to interleukin-1beta stimulation. Rat SMC-produced NGAL was present as mono- and homomeric forms in the cytosol and in a complex containing matrix metalloproteinase-9 (MMP-9) after secretion. In agreement with levels of NGAL, proteolytic activity of MMP-9 was markedly high in the intima of injured vessels and in the culture supernatant of activated intimal SMCs but was reduced in the vessels transduced with dnIKKbeta. The present study reveals a previously unrecognized vascular response to an-gioplastic injury, characterized by NF-kappaB-dependent expression of NGAL in vascular SMCs. Further-more, SMC-produced NGAL interacts with MMP-9, a mechanism by which NGAL may modulate MMP-9 proteolytic activity in the vascular repair process.

Analysis of porcine peripheral blood mononuclear cells proteome by 2-DE and MS: Analytical and biological variability in the protein expression level and protein identification

In this paper, we present the protein map corresponding to the porcine peripheral blood mononuclear cells (PBMC) to better understand the role of these cells in the pig immune system. To conform the map, the proteins were separated by 2-DE using a 5-8 range pH gradient in IEF and approximately 800 spots were detected. Due to the high level of indeterminate variability associates to the 2-DE, analytical and biological variances were analyzed. The analytical variance was calculated for 50 proteins in three replicate 2-DE gels from the same protein extract whereas the biological variance was determined by comparison of the patterns obtained for the same 50 proteins in different animals. Values of 15.13 and 33.70% were determined for analytical and biological variances, respectively. These average variances will provide a quantified and statistical basis for future proteomic studies directed to evaluate relevant quantitative changes in the biological response. A representative set of the major proteins was subjected to MALDI-TOF analysis and over 75% of the proteins were identified on the basis of their similarity with its human homologue proteins. A large number of cytoskeletal and metabolic proteins were found as well as some proteins related to cell mobility and immunological functions. Finally, other proteins implicated in the cell signaling process, transport or apoptosis were also identified giving a wide overview of the porcine PBMC protein map.

Cyclophilin C-associated Protein Is a Mediator for Fibronectin Fragment-induced Matrix Metalloproteinase-13 Expression

The function of cyclophilin C-associated protein (CyC-AP) on expression of extracellular matrix and matrix metalloproteinases (MMPs) was studied in CyC-AP-null mice. Fibronectin showed increased expression of the 53- and 29-kDa fragments in skin and wounds from CyC-AP-null mice. Type I collagen had an initial degraded pattern in the skin of CyC-AP-null mice, which did not occur in wild-type mice. MMP-3, MMP-13, MMP-14, and tumor necrosis factor-alpha (TNFalpha) had a higher expression in CyC-AP-null skin. During wound healing, MMP-13 and TNFalpha were stimulated to an even higher level, suggesting they are regulated by multiple factors. To understand the regulatory mechanisms of the up-regulated MMPs, the direct effects of TNFalpha, IL-1beta, 45-kDa fibronectin fragment (FN-45), and the 70-kDa fibronectin fragments (FN-70) on the expression of MMPs were studied. MMP-13 expression increased significantly in both CyC-AP-null and wild-type dermal fibroblasts after treatment with IL-1beta or with TNFalpha. However, MMP-13 expression did not increase in CyC-AP-null fibroblasts but did increase only in wild-type fibroblasts after FN-45 and FN-70 treatment. MMP-3 activation was induced by FN-45 and did not show a difference between CyC-AP-null and wild-type fibroblasts, suggesting different regulatory pathways for FN-45 on MMP-13 and MMP-3 expression. Our data are the first to demonstrate that deletion of CyC-AP can abolish fibronectin fragment-induced MMP-13 expression through an unknown mechanism. CyC-AP is an important factor for the regulation of MMP-13 expression.

Expression of the Protein Product of thePCPHProto-oncogene in Human Tumor Cell Lines

Expression of the Protein Product of the PCPH Proto-oncogene in Human Tumor Cell Lines. Exposure of Syrian hamster embryo fibroblasts to chemical carcinogens resulted in the oncogenic activation of the PCPH proto-oncogene by induction of a single base-pair deletion that generated a truncated PCPH oncoprotein (mutated PCPH). Recently, we isolated and characterized the cDNA for the human PCPH proto-oncogene and determined that in humans PCPH is a single-copy gene located in chromosome 14 (14q24.3). Pilot mRNA expression studies indicated that PCPH was expressed in the majority of normal organs tested, particularly in liver and kidney, but it appeared to be expressed either at low levels or not at all in tumor cells or cell lines derived from the high-expressing tissues. We have generated an antiserum against bacterial recombinant Syrian hamster PCPH. This antiserum recognizes both the normal and truncated, oncogenic Syrian hamster PCPH proteins and cross-reacts with the yeast, mouse, rat and human homologue proteins. Using this antibody, we have performed a study of PCPH expression in a larger sample of human neoplastic cell lines, including some derived from breast, nervous system, colon, lung and pancreas tumors. Results confirmed the frequent lack of PCPH expression in malignant cells and identified several immunoreactive forms of PCPH being differentially expressed in cells of diverse tissue origins.