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Peroxisome proliferators are non-genotoxic carcinogens which are purported to exert their effect on cells through their interaction with members of the nuclear hormone receptor family termed peroxisome proliferators activated receptors (PPARs). Nuclear hormone receptors are ligand-dependent intracellular proteins that stimulate transcription of specific genes by binding to specific DNA sequences following activation by the appropriate ligand. Studies indicate that PPARs are activated by peroxisome proliferators such as clofibric acid, nafenopin, and WY-14,643, as well as by some fatty acids.

Crystallin, Mu (CRYM) is a taxon-specific crystallin protein which binds NADPH and has sequence similarity to bacterial ornithine cyclodeaminases. CRYM doesn’t perform a structural role in lens tissue; instead CRYM binds thyroid hormone for possible regulatory or developmental roles. CRYM gene mutations are linked with autosomal dominant non-syndromic deafness. CRYM specifically catalyzes the reduction of imine bonds in brain substrates which may include cystathionine ketamine and lanthionine ketamine.

Modulator of apoptosis 1 (MOAP1), is a member of the PNMA family and contains one BH3-like domain and one RASSF1-binding domain. MOAP1 was recognized by its interaction with apoptosis regulator BAX protein. MOAP1 includes a Bcl-2 homology 3 (BH3)-like motif, which is essential for the association with BAX. In addition, once over expressed MOAP1 mediates caspase-dependent apoptosis.

Transmembrane protein PRRT2 holds a proline-rich domain in its N-terminal half. PRRT2 is known to be primarily expressed in brain and spinal cord in embryonic and postnatal stages. Alterations in this gene are the cause for paroxysmal kinesigenic dyskinesia. PRRT2 mutations were found in nearly 30% of sporadic PKC patients.

BRMS1 protein, a member of the mSin3a family of HDAC (histone deacetylase complexes), is mainly restricted to the nucleus. BRMS1 holds two coiled-coil motifs and a few imperfect leucine zipper motifs. BRMS1 reduces the metastatic potential, but not the tumorogenicity, of melanoma cell lines and human breast cancer. Alternative splicing creates two transcript variants encoding different isoforms.

Charged multivesicular body protein 6 (CHMP6) is a member of the SNF7 family. The CHMP6 protein is a core component of the endosomal sorting necessary for transport complex III (ESCRT-III) that is involved in multivesicular bodies (MVBs) formation and sorting of endosomal cargo proteins into MVBs. MVBs contain intraluminal vesicles (ILVs) which are produced by invagination and scission from the limiting membrane of the endosome and generally are transported to lysosomes facilitating degradation of membrane proteins, such as stimulated growth factor receptors, lysosomal enzymes and lipids.

Small Ubiquitin-like Modifiers (SUMOs) are a family of small, related proteins that can be enzymatically attached to a target protein by a post-translational modification process termed sumoylation. Unlike ubiquitination, which targets proteins for degradation, sumoylation participates in a number of cellular processes, such as nuclear transport, transcriptional regulation, apoptosis, and protein stability. All SUMO proteins share the conserved ubiquitin domain and the C-terminal diglycine cleavage/attachment site. Human SUMO2, also known as Sentrin2 and SMT3B is synthesized as a 95 amino acid (aa), 11 kDa propeptide that contains a two aa C-terminal prosegment, and an 18 aa N-terminal protein interacting region (aa 33 -50). Following prosegment cleavage, the C-terminal glycine is enzymatically attached to a lysine on a target protein. Human SUMO2 shares 100% sequence identity to SUMO-2 from mouse. SUMO2 also has very high sequence homology to SUMO3 and SUMO4, 86 % and 85%, respectively. SUMO2 shares only 44% sequence identity to SUMO1.

Trypsin inhibitor SPINK1 is secreted from pancreatic acinar cells into pancreatic fluid. SPINK1 has a role in inhibition of trypsin-catalyzed premature initiation of zymogens in the pancreas and the pancreatic duct. Alterations in SPINK1 gene are the cause for tropical calcific and pancreatitis hereditary pancreatitis.

Human Pin 1 is a peptidyl-prolyl cis/trans isomerase (PPIase) that interacts with NIMA and essential for cell cycle regulation Pin1 is nuclear PPIase containing a WW protein interaction domain, and is structurally and functionally related to Ess1/Ptf1, an essential protein in budding yeast. PPIase activity is necessary for Ess1/Pin1 function in yeast. Pin1 is thus an essential PPIase that regulates mitosis presumably by interacting with NIMA and attenuating its mitosis-promoting activity. Substrates of Pin1 include the mitotic regulators (Cdc25 phosphatase and NIMA, PLK I, Wee, and Myt1 kinases), several transcription factors like b-Catenin, c-Jun, and the tumor suppressor protein p53, and some specific proteins like the RNA Pol II, the cytoskeleton protein tau, and the G1/S protein Cyclin D1.

Proprotein Convertase Subtilisin/Kexin Type 1 Inhibitor (PCSK1N) takes part in the control of the neuroendocrine secretory pathway. PCSK1N inhibits prohormone convertase 1, which regulates the proteolytic cleavage of neuroendocrine peptide precursors. PCSK1Nslows down convertase-mediated processing of proopiomelanocortin and proenkephalin and also monitors the intracellular timing of PCSK1.

Cell surface glycoprotein MUC18 (MCAM), is an integral membrane glycoprotein which is part of the immunoglobulin superfamily. MCAM is related with a variety of carcinomas such as tumor progression, metastasis and is also implicated in embryonic neural development. In Addition, MCAM takes part in cell adhesion, as well as in cohesion of the endothelial monolayer at the intercellular junctions in vascular tissue.

ATPase inhibitory factor 1 (ATPIF1) attaches to the C-terminal region of a beta subunit of the F1-ATPase at low pH values and, through interference of the beta and gamma subunit interaction, ATPIF1 controls the activity of the F1 (the hydrophilic catalytic core), F0 (the membrane embedded protein channel) ATPase. ATPIF1 overexpression in a number of human carcinomas additionally reinforces its participation in oncogenesis and offers insight into the transformed metabolism of cancer cells, including the reprogramming of energy metabolism in relation to glycolysis. Endogenous F1F(o)-ATPase inhibitor curbing ATP depletion when the mitochondrial membrane potential drops below a threshold and the F1F(o)-ATP synthase begins hydrolyzing ATP to pump protons out of the mitochondrial matrix.

Immunity-related GTPase family M protein (IRGM) is essential for clearance of severe protozoan and bacterial infections. IRGM belongs to the p47 immunity-related GTPase family. IRGM serves in innate immune response possibly via regulation of autophagy. IRGM regulates proinflammatory cytokine production and inhibit endotoxemia upon infection and also has a part in macrophages adhesion and motility. Polymorphisms which modify the natural expression of the IRGM gene are associated with a susceptibility to Crohn's disease and tuberculosis.

Ubiquitin is a highly conserved 76 amino acid protein expressed in all eukariotes. Ub is found either in free form or conjugated to proteins as monomer or as chain of ubiquitin molecules. The most well characterized consequence of polyubiquitination is substrate degradation, while mono-ubiquitinated proteins are not degraded. Ubiquitin attachment to protein substrate is a complex process involving a ubiquitin activating enzyme (E1), a ubiquitin conjugating enzyme (E2) and a ubiquitin protein ligase (E3). The first ubiquitin moiety is transferred to the e-NH2 group of a Lys residue of the protein substrate to generate an isopeptide bond. In successive reactions, a poly ubiquitin chain is synthesized by processive transfer of additional activated moieties to Lys48 of the previously conjugated ubiquitin molecule. Ubiquitin K48R prevents the formation of poly ubiquitin chains via Lys48 linkages with mono ubiquitin molecules, avoiding the degradation of protein substrates.

Ring Finger Protein 114 (RNF114) is expressed in various tissues, including skin, CD4 lymphocytes and dendritic cells. RNF114, which contains 1 RING-type zinc finger, takes part in spermatogenesis.

Oncomodulin is a member of the superfamily of calmodulin proteins, otherwise known as the EF-hand proteins. It is a high-affinity calcium ion-binding protein. Oncomodulin is an oncodevelopmental protein which is found in early embryonic cells in the placenta and also in tumors.

STAT1 is a member of the Signal Transducers and Activators of Transcriptionfamily of transcription factors. STAT1 is involved in upregulating genes due to a signal by either type Ior type IIinterferons. In response to IFN-?stimulation, STAT1 forms homodimers or heterodimers with STAT3that bind to the GAS (Interferon-Gamma Activated Sequence) promoter element; in response to either IFN-? or IFN-?stimulation, STAT1 forms a heterodimer with STAT2that can bind the ISRE (Interferon Stimulated Response Element) promoter element. In either case, binding of the promoter element leads to an increased expression of ISG (Interferon Stimulated Genes).

The conserved 76 amino acid protein ubiquitin (Ub) regulates a host of intracellular processes through its enzymatic conjugation to other cellular proteins.
Ubiquitination occurs through sequential steps catalyzed by activating (E1), conjugating (E2), and ligase (E3) enzymes. The final step results in the formation of an isopeptide bond between Ub’s C-terminal glycine residue (G76) and a lysine residue of the target protein, although N-terminal ubiquitination is also known.
Outcomes of this modification include destabilization of the conjugated protein, altered protein trafficking and functional modulation.
After targeting the protein for specific localizations, ubiquitin is released from the substrate by deubiquitinating enzymes.
A mutant ubiquitin, having a Gly to Ala substitution at the C-terminus (G76A ubiquitin) supported several downstream reactions of the proteolytic pathway but inhibits the deubiquitination process.
As consequence, the Ub derivative becomes irreversibly conjugated to protein, shifting the equilibrium between the bound and unbound form in the direction of conjugation, at the expense of the free form.

Non-Metastatic Cells 4 or NME4, is a nucleoside diphosphate kinase located in the mitochondria, and is part of the NDK family of proteins. NME4 ais a very common enzyme that enhances transfer of gamma-phosphates, through a phosphohistidine as a intermediate, between dioxynucleoside tri- and diphosphates. NME4 is originated from the nm23 gene. NME4 has a crucial part in the creation of nucleoside triphosphates that are not ATP.

Leucine zipper down-regulated in cancer 1-like (LDOC1L) is a member of the LDOC1 family. LDOC1L is a nuclear protein containing a leucine zipper-like motif and a proline-rich region that shares noticeable similarity with an SH3-binding domain. LDOC1L localizes to the nucleus and is downregulated in certain cancer cell lines. LDOC1L is believed to regulate the transcriptional response mediated by the nuclear factor kB (NFkB).

GPN-loop GTPase 1 (GPN1) is a member of the GPN-loop GTPase family. GPN1 is a guanosine triphosphatase enzyme which has a role in DNA repair and may function in activation of transcription. Small GTPases, which share a biochemical mechanism, act as binary molecular switches and function in the cell is nucleocytoplasmic transport of both proteins and RNA. In addition, GPN1 establishs an interface between the RNA polymerase II enzyme and chaperone/scaffolding protein, proposing that it is essential to connect RNA polymerase II to regulators of protein complex formation. GPN1 may also be involved in nuclear localization of XPA.