β-Polymerase is a vertebrate cellular DNA polymerase involved in gap-filling synthesis during some types of genomic DNA repair. We report that a cloned human β-polymerase promoter in a transient ...expression assay is activated by p21
v-
ras
expression in NIH 3T3 cells. A decanucleotide palindromic element, GTGACGTCAC, at positions -49 to -40 in the promoter is required for this ras-mediated stimulation.
Previous studies have demonstrated the efficacy of two thymidine analogs, 5-iododeoxyuridine (IdUrd) and 5-bromodeoxyuridine (BrdUrd), as inducers of murine leukemia virus (MLV) synthesis in ...virus-negative cell clones derived from AKR mouse embryos. The results of screening other compounds, such as other base analogs, chemical carcinogens, and mutagens, demonstrate that these two thymidine analogs are by far the most efficient inducers of MLV synthesis in these cells. To obtain maximal activation of virus synthesis by the thymidine analogs, it was necessary to define both the optimal level of drug and time of exposure for each cell system.
The studies presented here indicate that incorporation of IdUrd or BrdUrd into cellular DNA plays a vital role in the activation of murine leukemia virus production in the AKR cell lines. (1) If DNA synthesis is blocked or decreased by cytosine arabinoside or serum depletion during the halogenated pyrimidine treatment, the proportion of cells activated is diminished. (2) When analog incorporation into DNA is blocked by simultaneous treatment with thymidine, no induction of virus occurs. (3) When analog incorporation into DNA is enhanced by simultaneous treatment with fluorodeoxyuridine, the proportion of cells induced to produce virus is significantly increased. (4) When cells containing analog-substituted DNA are irradiated with visible light or X-rays, the number of cells activated also increases.
This study was conducted to determine whether the perioperative administration of octreotide decreases the incidence of pancreatic anastomotic leak after pancreaticoduodenectomy for malignancy.
Three ...multicenter, prospective, randomized trials concluded that patients who receive octreotide during and after pancreatic resection have a reduction in the total number of complications or a decreased incidence of pancreatic fistula. However, in the subset of patients who underwent pancreaticoduodenectomy for malignancy, either no analysis was performed or no benefit from octreotide could be demonstrated.
A single-institution, prospective, randomized trial was conducted between June 1991 and December 1995 involving 120 patients who were randomized to receive octreotide (150 microg subcutaneously every 8 hours through postoperative day 5) or no further treatment after pancreaticoduodenectomy for malignancy. The surgical technique was standardized, and the pancreaticojejunal anastomosis was created using the duct-to-mucosa or invagination technique.
The two patient groups were similar with respect to patient demographics, treatment variables, and histologic diagnoses. The rate of clinically significant pancreatic leak was 12% in the octreotide group and 6% in the control group (p = 0.23). Perioperative morbidity was 30% and 25%, respectively. Patients who underwent reoperative pancreaticoduodenectomy had an increased incidence of pancreatic anastomotic leak, whereas those who received preoperative chemoradiation had a decreased incidence of pancreatic anastomotic leak.
The routine use of octreotide after pancreaticoduodenectomy for malignancy cannot be recommended.
Mutational Analysis of a ras Catalytic Domain Willumsen, Berthe M.; Papageorge, Alex G.; Kung, Hsiang-Fu ...
Molecular and cellular biology,
19/7/1/, Volume:
6, Issue:
7
Journal Article
Peer reviewed
Open access
We used linker insertion-deletion mutagenesis to study the catalytic domain of the Harvey murine sarcoma virus v-ras
H
transforming protein, which is closely related to the cellular ras
H
protein. ...The mutants displayed a wide range of in vitro biological activity, from those that induced focal transformation of NIH 3T3 cells with approximately the same efficiency as the wild-type v-rasH gene to those that failed to induce any detectable morphologic changes. Correlation of transforming activity with the location of the mutations enabled us to identify three nonoverlapping segments within the catalytic domain that were dispensable for transformation and six other segments that were required for transformation. Segments that were necessary for guanosine nucleotide (GDP) binding corresponded to three of the segments that were essential for transformation; two of the three segments share strong sequence homology with other purine nucleotide-binding proteins. Loss of GDP binding was associated with apparent instability of the protein. Lesions in two of the three other required regions significantly reduced GDP binding, while small lesions in the last required region did not impair GDP binding or membrane localization. We speculate that this latter region interacts with the putative cellular target of ras. The results suggest that transforming ras proteins require membrane localization, guanosine nucleotide binding, and an additional undefined function that may represent interaction with their target.
Circular DNA intermediates of Harvey murine sarcoma virus (Ha-MuSV) have been cloned in λ gtWES-λ B and shown to be capable of transforming mouse NIH 3T3 cells Hager, G. L., Chang, E. H., Chan, H. ...W., Garon, C. F., Israel, M. A., Martin, M. A., Scolnick, E. M. & Lowy, D. R. (1979) J. Virol. 31, 795-809. By using the cloned Ha-MuSV DNA insert as a parental genome, we have constructed a series of insertion-deletion mutants by inserting an octomer containing the Sal I linker sequence (G-G-T-C-G-A-C-C) into various regions of the Ha-MuSV genome after partial digestion with Hae III. After ligation into λ gtWES· λ B-Sal I vector molecules, the mutant Ha-MuSV DNAs were cloned. Fourteen insertion-deletion mutants have been mapped by restriction enzyme digestion, and their biological activities have been correlated with the locations of mutations. The mutants whose lesion mapped within 3.0 kilobases (kb) from the 3′-end of the Ha-MuSV genome retained full transforming ability. The mutants containing the Sal I linker insertion at 0.4 or 1.5 kb from the 5′-end also retained transforming ability, but the number of foci induced by the DNAs in transfection assays was greatly reduced. However, a mutant containing a deletion of 1.5 kb at the 5′-end and a mutant with a deletion of the sequences between 1.0 and 1.5 kb from the 5′-end completely lost their transforming potential. A model for the transforming region of Ha-MuSV is discussed. Furthermore, because Ha-MuSV sequences can be rescued from the mouse cells transformed by these mutants using Moloney murine leukemia virus as a helper virus, it implies that the in vitro modified DNAs may be converted into genuine mutant viruses.
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