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To compare the time course of in vitro expression of various proliferation-associated markers including Ki-67 antigen, transferrin receptors (TfR), and DNA polymerase α, six human tumour cell lines of different histological origin were studied under defined conditions. Proliferation markers were demonstrated by peroxidase/anti-peroxidase staining using specific monoclonal antibodies, and their expression was compared to results obtained from [H]-thymidine incorporation assays and cell counting. Expression of all proliferation markers began to increase during the lag phase, and occurred earlier than elevations of [H]dT incorporation and cell numbers were recorded. Maximum expression was observed before cell growth reached plateau phase. The time courses of expression of DNA polymerase and Ki-67 were almost identical. The closest correlation of [H]dT incorporation with time course of expression of proliferation-associated markers was observed, when intranuclear staining of DNA polymerase was analysed. TfR were expressed earlier than the polymerase and Ki-67. Since TfR were also found at remarkable levels in resting cells, they seem less proliferation-specific than Ki-67 and DNA polymerase. While in rapidly growing cell lines more than 95% of the cells expressed Ki-67, TfR, and more than 75% DNA polymerase in cell nuclei, a malignant melanoma and a pleural mesothelioma line displayed fewer than 35% of cells stained for DNA polymerase in cell nuclei during log phase. Determination of growth fractions by monoclonal antibodies may thus contribute to the prediction of chemoresistance by identifying quiescent cells that are not sensitive to S-phasespecific drugs. [ABSTRACT FROM AUTHOR]

Protein splicing is a precise post-translational process mediated by inteins. Inteins are intervening proteins that cleave themselves from a precursor protein while joining the flanking sequences. Here we report the N, C, and H chemical shift assignments of the intein from DNA polymerase II of Pyrococcus abyssi ( Pab PolII intein), which has been recombinantly overexpressed and isotopically labeled. The NMR assignments of Pab PolII intein are essential for solution structure determination and protein dynamics study. [ABSTRACT FROM AUTHOR]