ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
NRK cells infected with a temperature-sensitive, transformation-defective mutant of avian sarcoma virus (ASV), tsLA23, are transformed at 36°C, but at 40°C they behave as nontransformed cells because of the inactivation of the abnormally thermolabile pp60v-src product of the virus' transforming src gene. At 40°C, these tsLA23-NRK cells were arrested in G1/G0 by severe serum deprivation. They were induced to enter G1, initiate DNA synthesis 7 or 10 hours later, and then divide as (1) nontransformed cells by adding serum or platelet-derived growth factor (PDGF) at 40°C, or (2) transformed cells by lowering the temperature to a pp60v-src-activating 36°C without adding exogenous growth factor(s). The level of pp60v-src kinase activity rose dramatically in these serum-deprived cells within 30 minutes of lowering the temperature to the permissive 36°C, and it fell just as rapidly when the cells were returned to the restrictive 40°C. As little as a 2-hour exposure to 36°C, with an attendant 2-hour burst of pp60v-src kinase activity, was enough to stimulate serum-deprived tsLA23-NRK cells to transit G1 and initiate DNA replication, but not to divide. Much more prolonged pp60v-src activity was needed for these serum-deprived cells to complete their cycle and divide. The prereplicative development of quiescent tsLA23-NRK cells stimulated by serum or PDGF was accompanied by greatly increased protein synthesis and slightly decreased protein degradation, but the pp60v-src-stimulated cells progressed through G1 and initiated DNA replication without appreciably affecting the protein synthetic machinery of the cell. The cells stimulated by the mitogenic action of pp60v-src, like the cells stimulated by serum, needed to activate early prereplicative genes in order to initiate DNA replication. The needed RNA transcripts induced by serum and pp60v-src were produced with comparable efficiency, although it took longer for pp60v-src-stimulated cells to translate these transcripts and to initiate DNA replication, probably because of their unstimulated protein-synthetic machinery.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041200205
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