Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The protective effect of Mr 70,000 heat shock protein (HSP-70) during thermotolerance has been previously observed. However, it is not known what cellular processes or components may be protected by this protein during the tolerance state. In the studies reported here, the protective effects of purified HSP-70, the nonspecific heat-stable proteins fetuin and trypsin inhibitor (ovomucoid), and other proteins and agents such as bovine serum albumin, D2O, or glycerol on protein and DNA synthesis during heating were investigated in vitro. In vitro protein synthesis at 30, 40, and 42 degrees C was measured by globin mRNA translation. Protein synthesis was inhibited 40 to 70% when incubated for 60 min at 40 and 42 degrees C. However, protein synthesis was protected when either fetuin or ovomucoid was present during protein synthesis at elevated temperatures. The protection was concentration dependent. The HSP-70 purified from Chinese hamster (HA-1) cells was also able to confer protection to the translation system, but at much lower concentrations than either fetuin or ovomucoid. Other proteins, such as bovine serum albumin, or other agents, such as D2O or glycerol which are known protectors of cellular survival during heating, did not protect the translation system. Similar experiments were performed with DNA synthesis in vitro. Purified DNA polymerase alpha was added to the activated calf thymus DNA in an in vitro replication system. A temperature of 46 degrees C for 60 min inhibited replication by 40%. Addition of heat-stable proteins, purified HSP-70, bovine serum albumin, D2O, or glycerol did not confer protection to the replication system. These studies provide new evidence that HSP-70 may confer protection to a component of the protein synthesis machinery during thermotolerance.
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PMID:Effects of heat shock proteins (Mr 70,000) on protein and DNA synthesis at elevated temperatures in vitro. 246 56

Two enzymes of base excision repair (BER), uracil DNA glycosylase (UDG) and DNA polymerase beta (beta pol), from HeLa cells co-eluted from Superose 12 FPLC columns. The UDG was completely displaced from 150-180-kDa fractions to 30- 70-kDa fractions by brief treatment with 0.5 N NaCl, pH 3.0, as expected when protein-protein associations are disrupted, but beta pol was not displaced by this treatment. UDG was not essential to the presence of beta pol in the 150-180-kDa enzyme complex. beta pol and UDG apparently reside in separate but co-eluting structures. Immunoaffinity chromatography showed that the association of UDG and beta pol was accounted for by attachment in common to DNA and that the association was abolished by eliminating DNA. Evidence for base excision repairosomes containing UDG and beta pol in protein-protein assemblies was not found. However, UDG and human AP endonuclease (HAP1) were associated with HSP70 and HSP27, which are present in 150-180-kDa and 30-70-kDa proteins of cell sonicates. The association of HSPs with BER enzymes was confirmed by hydroxyl radical protein-protein footprinting and immunoaffinity tests. The association of HSPs and BER enzymes is a novel finding. HSP binding may account for the presence of BER enzymes in the two large size class fractions and HSPs may have functional roles in BER.
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PMID:Heat-shock proteins associated with base excision repair enzymes in HeLa cells. 1062 18

We present here computer generated model of N-terminal fragment, amino acids (aa) 36-245, of a Plasmodium vivax heat shock metalloprotease called PVHSP28, whose gene was cloned and characterised earlier. The fragment showed homology with HSPs from many organisms, including Escherichia coli and Haemophilus influenzae. PVHSP28 had the signature sequence 'HEXXH' and 'EXXXD' of Zinc metalloproteases. Being the first malarial HSP possessing metalloprotease activity, PVHSP28 is an ideal target for the design of new anti-malarial drugs. However, except for a small region (aa 62-132) which had 24.6% sequence similarity with 1TAQ (a DNA polymerase), it did not show sequence similarity with any published structures in protein data bank. Hence it could not be modelled using any automated modeling programs. We modelled 36-245 aa of PVHSP28 using predicted secondary structure as well as experimentally determined and predicted properties of the protein on the basis of its amino acid sequence, using various Internet tools and in-house package MODEL. The model was energy minimised using Sander's module of AMBER 5.0, working on a Silicon Graphics machine, with all atom force field.
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PMID:Computer modeling of small heat-shock metalloprotease of the human malaria parasite Plasmodium vivax. 1169 26

Podophyllum hexandrum Royale (Himalayan mayapple), a high-altitude Himalayan plant, has been shown to provide over 80% whole-body radioprotection in mice. To investigate the radioprotective potential of P. hexandrum at the molecular level, expression patterns of various proteins associated with apoptosis were studied in the spleen of male Swiss albino strain A mice by immunoblotting. Treatment with P. hexandrum [200 mg/kg of body weight; an ethanolic 50% (w/v) extract delivered intraperitoneally] 2 h before irradiation resulted in MAPKAP (mitogen-activated protein kinase-activated protein) kinase-2 activation along with HSF-1 (heat-shock transcription factor-1), leading to up-regulation of HSP-70 (heat-shock protein-70) as compared with sham-irradiated (10 Gy) mice. Strong inhibition of AIF (apoptosis-inducing factor) expression was observed in the mice treated with P. hexandrum 2 h before irradiation as compared with the sham-irradiated group. Inhibition in the translocation of free NF-kappaB (nuclear factor kappaB) from cytoplasm to nucleus was observed upon P. hexandrum pretreatment 2 h before irradiation when compared with radiation-treated mice. P. hexandrum pre-treatment (2 h before irradiation) resulted in inhibition of NF-kappaB translocation, and the expression of tumour suppressor protein p53 was observed to be down-regulated as compared with sham-irradiated control. An increase in the expression of proteins responsible for cell proliferation [Bcl-2 (B-cell chronic lymphocytic lymphoma 2), Ras-GAP (Ras-GTPase-activating protein) and PCNA (proliferating cell nuclear antigen)] was observed in the P. hexandrum-pretreated irradiated mice as compared with sham-irradiated controls. Caspase 3 activation resulted PARP [poly(ADP-ribose) DNA polymerase] cleavage, and DNA degradation was strongly inhibited in the mice treated with P. hexandrm (+/-irradiation) as compared with the mice treated with radiation (+/-heat shock). The present study thus clearly demonstrated that P. hexandrum extract provides protection from gamma-radiation by the modulation of expression of proteins associated with cell death.
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PMID:Podophyllum hexandrum (Himalayan mayapple) extract provides radioprotection by modulating the expression of proteins associated with apoptosis. 1576 43