The eukaryotic polypeptide chain releasing factor (eRF3/GSPT) carrying the translation termination signal to the 3'-Poly(A) tail of mRNA. Direct association of erf3/GSPT with polyadenylate-binding protein.

The mammalian GTP-binding protein GSPT, whose carboxyl-terminal sequence is homologous to the eukaryotic elongation factor EF1alpha, binds to the polypeptide chain releasing factor eRF1 to function as eRF3 in the translation termination. The amino-terminal domain of GSPT was, however, not required for the binding. Search for other GSPT-binding proteins in yeast two-hybrid screening system resulted in the identification of a cDNA encoding polyadenylate-binding protein (PABP), whose amino terminus is associating with the poly(A) tail of mRNAs presumably for their stabilization. The interaction appeared to be mediated through the carboxyl-terminal domain of PABP and the amino-terminal region of GSPT. Interestingly, multimerization of PABP with poly(A), which is ascribed to the action of its carboxyl-terminal domain, was completely inhibited by the interaction with the amino-terminal domain of GSPT. These results indicate that GSPT/eRF3 may play important roles not only in the termination of protein synthesis but also in the regulation of mRNA stability. Thus, the present study is the first report showing that GSPT/eRF3 carries the translation termination signal to 3'-poly(A) tail ubiquitously present in eukaryotic mRNAs.     

Effects of macrophyte harvesting on the water quality and bottom environment of Lake Biwa,Japan

Limnology - Appropriate management of macrophyte biomass via harvesting is crucial for maintaining eutrophic inland waters. However, information on the effects of macrophyte harvesting on the...     

Mycoplasma pulmonis Arthritis in Congenitally Athymic (Nude) Mice

Histopathological examinations were performed on arthritic joints and other organs of strain BALB/cA nu/nu and nu/+ mice intravenously injected with Mycoplasma pulmonis strain m53. In both groups of mice suffering from polyarthritis, acute inflammatory lesions with infiltration of polymorphonuclear leukocytes in the synovia and periarticular tissues were observed one to two weeks after injection. In nu/nu mice, the acute inflammation appeared repeatedly up to 20 weeks after inoculation, when the experiment was terminated, and furthermore, extensive synovial and periarticular necrosis were characteristically present after the 4th week. Only a small number of lymphocytes and plasma cells were in the lesions. In nu/+ mice, after the early acute inflammation of arthritis, relapses of the infiltration of polymorphonuclear leukocytes were also observed in some mice in and after the 10th week. In addition, infiltration of lymphocytes and plasma cells was substantial after the 15th week. Focal necrosis was sometimes found in the liver of nu/nu mice. Perivascular infiltration of small lymphocytes and plasma cells was found in the lungs, liver and kidney of nu/+ mice in and after the 15th week. Repair mechanisms of injured articular tissues in nu/nu mice were histopathologically poor, while those in nu/+ mice seemed to be progressive and quite similar to those reported by many investigators for mice with the thymus intact. The histopathological differences are discussed in respect to the thymus-dependent immune responses.     

Mutability of constitutive heterochromatin (C-bands) during eukaryotic chromosomal evolution and their cytological meaning.

A quantitative analysis of the alterations of constitutive heterochromatin in eukaryotic chromosomal evolution was attempted using the accumulated C-banding data available for mammals, amphibians, fish, ants, grasshoppers, and plants. It was found that these eukaryotes could be classified into two types by their C-banding patterns: 1) Type I included mammals, fish, and ants, and 2) Type II included amphibians, grasshoppers, and plants. C-bands were rather scarce in Type I eukaryote chromosomes and were found around the pericentromeric region when present at all, whereas the predominance of interstitial or terminal C-bands was found in Type II eukaryote chromosomes. The Type I and II C-banding patterns can best be interpreted by assuming that in the former group of eukaryotes the saltatory increase in constitutive heterochromatin occurs preferentially at the pericentromeric regions of telocentric chromosomes induced by centric fission, with C-bands being eliminated almost completely by centric fusion and/or pericentric inversion. On the other hand, C-bands appear in the Type II eukaryotes both interstitially and in the telomeric regions of chromosomes, and there may be no effective mechanism to eliminate these bands once they are integrated.     

Immunohistochemical distribution of the antigenic determinants detected by monoclonal antibodies to carcinoembryonic antigen

By using four distinct monoclonal antibodies to CEA, the molecular profile of which was clarified in our accompanying companion paper, immunohistochemical distribution of the antigenic determinants on both cancerous and noncancerous tissues as well as fetal tissues was studied with the use of the immunoperoxidase method. All of the monoclonal antibodies recognize different antigenic determinants on the tissue section. None of the antibodies stained granulocytes in the peripheral blood or in the normal liver tissues tested. Three of our monoclonal antibodies stained columnar epithelial cells in morphologically normal colonic mucosa; however, monoclonal antibody YK024 did not stain them. This antibody was also found to be unreactive with intestinal metaplasia lesions of the stomach, but reacted with a 16-wk-old fetal stomach as well as with cancerous parts of the colon and of the stomach. Moreover, it was found that this monoclonal antibody mainly reacted with moderately or poorly differentiated adenocarcinoma lesions of the colon and the stomach. Periodic acid treatment in this study, together with trypsin treatment on the antigen as described in our accompanying companion paper, may suggest that this antibody recognizes the carbohydrate antigenic determinant in nature.