Proliferation-sensitive nuclear phosphoprotein "dividin" is synthesized almost exclusively during S phase of the cell cycle in human AMA cells.

Abstract

Studies of the polypeptides synthesized by normal and transformed human cultured cells under a variety of physiological conditions have revealed a basic 54-kDa protein NEPHGE 1Oa, whose rate of synthesis is sensitive to changes in the rate of cell proliferation. This nuclear phosphoprotein, which we have termed "dividin" (present only in populations of cells committed to divide), is synthesized almost exclusively during the S phase of the cell cycle of transformed human amnion cells (AMA). Dividin synthesis is first detected late in G, near the G1/S transition border, reaches a maximum late in S phase, and declines thereafter. As expected for an S phase-specific protein, no detectable synthesis of dividin was observed in growth-arrested normal human cultured cells of epithelial and fibroblast origin. These findings suggest a role for this protein in events leading to DNA replication and cell division.Working with the hypothesis that somatic cell transformation may be due to the abnormal expression of normal genes, we began a detailed study of the overall patterns of gene expression at the level of protein synthesis in normal and transformed human cells to identify proteins that may be involved in the control of cell proliferation (1-4). The ultimate goal of these studies is to elucidate the pathway(s) that controls cell proliferation in normal human cells and, hence, to determine the means by which alterations of the pathway(s) lead to abnormal growth and/or neoplastic transformation and cancer. To date, several growth rate-and transformation-sensitive polypeptides have been identified using high-resolution twodimensional (2D) gel electrophoresis (refs. 2 and 3 and references therein). Of these, the proliferation-sensitive nuclear protein cycin (2)(3)(4)(5)(6), also termed proliferating cell nuclear antigen (PCNA) (7,8), is one of the most striking as the rate of synthesis of this protein increases specifically during S phase (9-11), and its activity may be associated with some specific aspect of DNA replication (12)(13)(14)(15)(16)(17)(18).In this communication we present evidence showing that the proliferation-sensitive 54-kDa human nuclear basic phosphoprotein NEPHGE 10a [ Fig. 1 MATERIALS AND METHODSCells. All the cells used in this study were grown in Dulbecco's modified Eagle's medium (DMEM) containing 10% (vol/vol) fetal calf serum and antibiotics (penicillin at 100 units/ml, streptomycin at 50 ,ug/ml).Cell Cycle Studies. Mitotic AMA cells were obtained by mechanical detachment essentially as described by Terasima and Tolmach (22). Two 250-ml flasks containing 1-2 x 106 cells per flask were used. The homogeneity of the collected cells was assessed by phase-contrast microscopy. Cells for [35S]methionine labeling were plated in microtiter wells (96-well plates, Nunc), while those for immunofluorescence were plated on round glass coverslips. Entrance of the cells into S phase was determined by indirect immunofluorescence using PCNA antibodies specific for cyclin (17,23).Quiescent Cultures. MRC-5 hum...

The nuclear matrix protein, numatrin (B23), is associated with growth factor-induced mitogenesis in Swiss 3T3 fibroblasts and with T lymphocyte proliferation stimulated by lectins and anti-T cell antigen receptor antibody.

“…EVERAL nuclear proteins including cyclin/PCNA (6), p53 (21), dividin (7), and proteins encoded by protooncogenes such as c-myc, c-myb, and c-fos (review reference 2), have been implicated in processes associated with the regulation of cellular growth. Recently, we have described and characterized a nuclear protein at 40 kD/pI-5 whose synthesis was found to be rapidly induced in murine B lymphocytes after stimulation with various mitogens (12).…”

Phase-Specific Polypeptides and Poly(A)+ RNAs during the Cell Cycle in Synchronous Cultures of Catharanthus roseus Cells

“…Many studies have been undertaken to examine the changes in protein patterns through which the sequential action of genes during the cell cycle is reflected, and to demonstrate that genes involved in cell proliferation are expressed transiently during the cell cycle. Two-dimensional gel electrophoresis has revealed the presence of several phase-specific proteins in mammalian cells which appear in the G2 phase (1) or which are synthesized in the S phase (10) and the G2/M phase (41). There are also reports (8,15,29) that no unique proteins are synthesized during the cell cycle in HeLa cells and yeast.…”