Life and Medical Sciences
Cell & Developmental Biology
Wiley InterScience Backfile Collection 1832-2000
Analysis of gene expression following stimulation of growth-arrested cells has beei the main approach for identification of growth-associated genes. Since the activation of these gene sequences is dependent on both the stimulatory agent and theitate of quiescence of the cell, the activation and role of the same genes may be entirely different in non-growth arrested, actively proliferating cells. We have addressed the question of growth-associated gene expression during active growth by analyzing gene expression during G-1 of cells which have jusl exited mitosis without first leaving the cell cycle. We were able to isolate, by a non-inductive, drug free system, a population of highly synchronized Swiss 3T3 cells within mitos is (〉90%) in numbers sufficient to determine the pattern of expression pf a large number of representative growth-associated genes. Our results show that after replating the mitotic ceils into conditioned medium: (1) growth-associated gene expression is not constant during G-1 of actively proliferating cells, and (2) while a number of genes (e.g., JE, c-myc, ODC, p53, and histone) exhibited patterns of expression similar to that reported in the quiescent systems, others (e.g., nur-77, vimentin, calcyclin) exhibited patterns which were completely different. From these results, we can begin to construct a temporal map of G-1 progression during active growth.
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