Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phenotypes of the cells developing into small colonies after days of primary culture of adult rat hepatocytes in serum-free modified Dulbecco Modified Eagles' medium containing 10 mM nicotinamide and 10 ng/ml epidermal growth factor were analyzed immunocytochemically, cytochemically and ultrastructurally. Albumin, cytokeratin 8 and 18 were seen by immunocytochemical techniques in the cells of the small colonies at Day 6. Transferrin, alpha 1-antitrypsin, ceruloplasmin, and haptoglobin, proteins secreted by mature hepatocytes, were faintly stained in these cells as was alpha-fetoprotein. These proteins were secreted into the culture medium as evidenced by immunoblot analysis. gamma-Glutamyltransferase, alkaline phosphatase and glucose 6-phosphatase were not present in the cells of the small colonies as well as the surrounding hepatocytes at Day 6 of culture. In addition, ultrastructural examinations of the cells in the small colonies indicated that these cells not only had many characteristic mitochondria and desmosomes, but also a few small peroxisomes. Such cells, even after 20 days in culture were proliferating, as evidenced by the intranuclear presence of the proliferating cell nuclear antigen. The potential relation of these cells to hepatocytes which may serve as the principal reserve for replicating hepatocytes is discussed.
Virchows Arch B Cell Pathol Incl Mol Pathol 1992
PMID:Characteristics of small cell colonies developing in primary cultures of adult rat hepatocytes. 127 92

The role of DNA polymerases in the replication of SV40 DNA was studied using a T-antigen-dependent assay supplemented with a human KB cell extract. Inhibition of DNA polymerase alpha by addition of aphidicolin or monoclonal antibodies prevented DNA synthesis, confirming the requirement for this enzyme in replication. The replication process was unaffected by ddTTP at a concentration (5 microM) inhibitory to DNA polymerases beta and gamma, however, higher concentrations of ddTTP (200 microM) caused an apparent accumulation of relaxed circular plasmid with a concomitant decrease in DNA synthesis. An analysis of this replication intermediate indicated that it was formed during the replication reaction and that the replicative cycle was nearly complete. A kinetic study of ddTTP inhibition strongly suggested DNA polymerase epsilon (PCNA-independent DNA polymerase delta) was the target of the inhibitor and that this enzyme functions during the final stages of DNA replication.
Mol Cell Biochem 1992 Mar 04
PMID:Dideoxynucleoside triphosphates inhibit a late stage of SV40 DNA replication in vitro. 131 27

A number of proteins have been isolated from human cells on the basis of their ability to support DNA replication in vitro of the simian virus 40 (SV40) origin of DNA replication. One such protein, replication factor C (RFC), functions with the proliferating cell nuclear antigen (PCNA), replication protein A (RPA), and DNA polymerase delta to synthesize the leading strand at a replication fork. To determine whether these proteins perform similar roles during replication of DNA from origins in cellular chromosomes, we have begun to characterize functionally homologous proteins from the yeast Saccharomyces cerevisiae. RFC from S. cerevisiae was purified by its ability to stimulate yeast DNA polymerase delta on a primed single-stranded DNA template in the presence of yeast PCNA and RPA. Like its human-cell counterpart, RFC from S. cerevisiae (scRFC) has an associated DNA-activated ATPase activity as well as a primer-template, structure-specific DNA binding activity. By analogy with the phage T4 and SV40 DNA replication in vitro systems, the yeast RFC, PCNA, RPA, and DNA polymerase delta activities function together as a leading-strand DNA replication complex. Now that RFC from S. cerevisiae has been purified, all seven cellular factors previously shown to be required for SV40 DNA replication in vitro have been identified in S. cerevisiae.
Mol Cell Biol 1992 Jan
PMID:Identification of replication factor C from Saccharomyces cerevisiae: a component of the leading-strand DNA replication complex. 134 62

The influence of DNA polymerase (pol) alpha and DNA primase on SV40 DNA replication was examined in both the monopolymerase and dipolymerase systems. The synthesis of oligoribonucleotides in the monopolymerase and dipolymerase systems, followed by pulse labeling with deoxynucleoside triphosphates, yielded short Okazaki fragments approximately 35 nucleotides in length that were chased into full-length Okazaki fragments with time. In the presence of activator 1 and proliferating cell nuclear antigen (PCNA), but no pol delta, these short fragments hardly increased in size with time. DNA fragments of similar size (approximately 35 nucleotides) were previously observed in SV40 replication reactions carried out with crude extracts of HeLa cells in the presence of antibodies directed against PCNA (Bullock, P. A., Seo, Y.S., and Hurwitz, J. (1991) Mol. Cell. Biol. 11, 2350-2361). Thus, the pol alpha-primase complex appears to act processively for only a short distance. At high levels of pol alpha and primase, both short and long DNA products were formed in both systems. In the presence of limiting amounts of pol alpha and excess primase, the monopolymerase system inefficiently yielded longer length Okazaki fragments than those formed with excess pol alpha and primase, whereas the dipolymerase system yielded both short and long DNA fragments. In the presence of limiting amounts of primase and excess pol alpha, long products were formed in both systems, and virtually no short products accumulated. Thus, the ratio between the polymerase and primer ends available controls the size of the nascent product DNA strands. We examined whether PCNA, the T4 phage-encoded gene product 45 (T4 gp45), and the Escherichia coli beta subunit of DNA polymerase III (dnaN gene product) supported SV40 DNA replication and the elongation of single-stranded DNA-binding protein-coated singly primed DNA in reactions catalyzed by pol delta, T4 DNA pol, and E. coli DNA pol III*, respectively. In the presence of T4 gp44/62 and T4 gp32 (but not human single-stranded DNA-binding protein isolated from HeLa cells), T4 DNA pol was weakly activated by PCNA and the beta subunit in lieu of T4 gp45 in the elongation of singly primed phi X174 DNA. However, the other systems were specific for their analogous auxiliary factors. This specificity indicates the importance of protein-protein interactions.
 ...
PMID:The replication of DNA containing the simian virus 40 origin by the monopolymerase and dipolymerase systems. 134 4

In eukaryotic cells, nucleus-cytoplasm exchanges play an important role in genomic regulation. We have analyzed the localization of four nuclear antigens in different growth conditions: two replicative proteins, DNA polymerase alpha and proliferating cell nuclear antigen (PCNA), and two oncogenic regulatory proteins, c-Myc and c-Fos. A kinetic study of subcellular localization of these proteins has been done. In cultures in which cells were sparse, these proteins were detected in the nucleus. When proliferation was stopped by the high density of culture cells or by serum starvation, these proteins left the nucleus for the cytoplasm with different kinetics. DNA polymerase alpha is the first protein to leave the nucleus, with the PCNA protein, c-Fos, and c-Myc leaving the nucleus later. In contrast, during serum stimulation c-Fos and c-Myc relocalize into the nucleus before the replicative proteins. We also noticed that in sparse cell cultures, 10% of the cells exhibit a perinuclear staining for the DNA polymerase alpha, PCNA, and c-Myc proteins but not for c-Fos. This peculiar staining was also observed as an initial step to nuclear localization after serum stimulation and in vivo in Xenopus embryos when the G1 phase is reintroduced in the embryonic cell cycle at the mid-blastula stage. We suggest that such staining could reflect specific structures involved in the initiation of the S phase.
Mol Cell Biol 1992 Aug
PMID:Comparative analysis of the intracellular localization of c-Myc, c-Fos, and replicative proteins during cell cycle progression. 135 52

c-fos, a proto-oncogene regulating the transcription of many genes, plays a critical role in the cell cycle and differentiation and may be involved in the regulation of inflammation in asthma. Very low levels of c-fos are detectable in most human cells, and its expression is rapidly and transiently increased by multiple factors, some of which are involved in the airways inflammation of asthma (histamine, eicosanoids, and cytokines). The presence of c-fos protein, as detected by immunofluorescence, and the immunoreactivity of PCNA, a cell proliferation marker, were examined in bronchial biopsies obtained from 12 asthmatics and 10 normal subjects. Biopsies of eight of 12 asthmatics expressed c-fos versus none of 10 normal subjects. The expression was heterogeneous and localized to cells positive for anti-cytokeratin monoclonal antibody, indicating their epithelial origin. On the other hand, PCNA immunoreactivity was only observed in one asthmatic and one control subject but it was not related with c-fos expression. This study demonstrates the induction of c-fos in epithelial cells of asthmatics, suggesting a role for this proto-oncogene in activation rather than in proliferation.
Am J Respir Cell Mol Biol 1992 Aug
PMID:c-fos proto-oncogene expression in bronchial biopsies of asthmatics. 135 73

By using a complementation assay that enabled DNA polymerase delta and DNA polymerase epsilon to replicate a singly-DNA primed M13 DNA in the presence of proliferating cell nuclear antigen (PCNA) and Escherichia coli single-stranded DNA binding protein (SSB), we have purified from calf thymus in a five step procedure a multipolypeptide complex with molecular masses of polypeptides of 155, 70, 60, 58, 39 (doublet), 38 (doublet) and 36 kDa. The protein is very likely replication factor C (Tsurimoto, T. and Stillman, B. (1989) Mol. Cell. Biol. 9, 609-619). This conclusion is based on biochemical and physicochemical data and the finding that it contains a DNA stimulated ATPase which is under certain conditions stimulated by PCNA. Together RF-C, PCNA and ATP convert DNA polymerases delta and epsilon to holoenzyme forms, which were able to replicate efficiently SSB-covered singly-DNA primed M13 DNA. Calf thymus RF-C could form a primer recognition complex on a 3'-OH primer terminus in the presence of calf thymus PCNA and ATP. Holoenzyme complexes of DNA polymerase delta and epsilon could be isolated suggesting that these enzymes directly interact with the auxiliary proteins in a similar way. Under optimal replication conditions on singly-DNA primed M13 DNA the DNA synthesis rate of DNA polymerase delta was higher than of DNA polymerase epsilon. Based on these functional date possible roles of these two DNA polymerases in eukaryotic DNA replication are discussed.
 ...
PMID:Calf thymus RF-C as an essential component for DNA polymerase delta and epsilon holoenzymes function. 135 54

Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) has been suggested as a new approach for determining proliferative activity in paraffin-embedded tissue. In a prospective study PCNA immunostaining was performed in 284 colorectal biopsies using monoclonal antibodies 19F4 (Ogata et al. 1987) and PC10 (Waseem and Lane 1990) and compared with the Ki67 method. From each site three biopsies were taken and a variety of fixation regimens for frozen and paraffin-embedded samples tested. For frozen biopsies methanol fixation at -20 degrees C proved best. In paraffin sections PCNA could be detected after methacarn fixation as well as after controled fixation at 4 degrees C in 4% paraformaldehyde for 1 h and in most biopsies routinely fixed with 10% formalin. However, the latter fixation regimens revealed additional PCNA-positive cells in the normal superficial colonic mucosal epithelium. Although the percentage of cells positive for PCNA was generally lower than for Ki67, the rates correlated in a highly significant fashion, both in frozen methanol-fixed biopsies, and in paraformaldehyde-fixed paraffin-embedded samples. PCNA immunohistochemistry revealed a similar proliferative activity in different parts of the large bowel. A higher proliferative activity was found in inflamed mucosa, adenomas, carcinomas and even in normal mucosa from patients with colorectal neoplasms. In routinely fixed biopsies, the monoclonal antibody PC10 was superior to 19F4 because of considerably less background staining. However, in the routine material only a rough estimate of the proliferative activity was possible by PCNA immunohistochemistry using these antibodies, because unpredictable numbers of non-S-phase cells were also stained.(ABSTRACT TRUNCATED AT 250 WORDS)
Virchows Arch B Cell Pathol Incl Mol Pathol 1992
PMID:Analysis of proliferative activity in colorectal mucosa by immunohistochemical detection of proliferating cell nuclear antigen (PCNA). Methodological aspects and application to routine diagnostic material. 135 1

DNA polymerase epsilon was purified to near homogeneity from human placenta. The enzyme has one subunit (170 kDa, sedimentation coefficient 8.2S), intrinsic 3'-5'-exonuclease activity, it is independent on PCNA and high processivity on poly(dA)-oligo(dT) template-primer without PCNA. It was shown, that the enzyme incorporates 3'-amino-2',3'-dideoxythymidine 5'-triphosphate in DNA, after that synthesis is stopped. Simultaneously DNA polymerase alpha was purified.
Mol Biol (Mosk)
PMID:[A method of isolation and properties of DNA-dependent DNA-polymerase epsilon from human placenta]. 147 Jan 82

The atrial and ventricular surfaces of the mitral valve are lined by endothelial cells termed endocardial cells, while the valve stroma contains interstitial cells. Bovine mitral valve organ cultures were immunoperoxidase-stained for Factor VIII RAg, alpha smooth muscle actin, and PCNA/cyclin in order to identify the cell types involved in mitral valve wound repair. Factor VIII RAg is a well-characterized endothelial cell marker, alpha smooth muscle actin is an indicator of smooth muscle differentiation and PCNA/cyclin is a marker for S phase. Bovine mitral valve endocardium was Factor VIII RAg positive and remained positive after culturing for 6 days (n = 7). Mitral valve interstitial cells were Factor VIII RAg negative and positive for alpha smooth muscle actin. By 6 days in culture, the lateral edges of the preparations, where the tissue was originally dissected from the mitral valve leaflet, were covered by multiple layers of cells. These cells were Factor VIII RAg negative (n = 7), and hence not endocardial, but were alpha smooth muscle actin positive like interstitial cells. Interstitial cells subjacent to the lateral edges were negative for PCNA/cyclin in uncultured preparations (n = 5), but positive in 12 out of 15 specimens cultured for 6 days. The results suggest that mitral valve interstitial cells are responsible for the repair process seen in the lateral edges of mitral valve organ cultures.
J Mol Cell Cardiol 1992 Jan
PMID:Bovine mitral valve organ culture: role of interstitial cells in repair of valvular injury. 153 92


1 2 3 4 5 6 7 8 9 10 Next >>