Biomedical subjects
Publications and source records attributed to L McReynolds.
EcoRI fragments of the natural ovalbumin gene were cloned and studied by hybridisation with mature ovalbumin mRNA, electron microscopy, restriction enzyme mapping and limited sequence analysis. The structural gene sequences coding for ovalbumin were found to be separated into eight sequentially orientated pieces by seven intervening sequences of various lengths.
The complete sequence of chicken ovalbumin mRNA is presented; it is 1,859 residues long, excluding its terminal 'cap' and poly(A). The region coding for ovalbumin lies close to the 'cap' but is separated from the poly(A) by an extensive 3' noncoding region of 637 nucleotides which may have no function that is precisely dependent on its sequence.
We have found Chinese Hamster Ovary cells, cultured in suspension, are subject to growth control by serum. When suspended in medium containing 0.5% serum the cells becomes reversibly arrested in the beginning of the G1 phase of the cell cycle and can be maintained in this viable, nonproliferating state for several days. This system was used to examine the regulation of protein synthesis with growth rate. In particular, the experiments addressed the question whether mRNA content is the principal controlling factor determining the rate of protein synthesis. The rate of leucine incorporation in resting cells in low serum is 2-to 2.5-fold lower than that of cells growing in 10% serum. The steady-state number of cytoplasmic poly A (+) RNA molecules shows a proportional decrease, consistent with it being a determining factor controlling the rate of protein synthesis. Furthermore, the rate of production of poly A (+) and poly A (-) RNA appears to be regulated coordinately. Regulation of the rate of initiation of translation would result in fewer ribosomes bound per active message and/or a lower proportion of total mRNA's being active. Our measurements indicate that the fraction of cytoplasmic poly A (+) mRNA in polyribosomes and the relative degree of loading of each active poly A(+) mRNA with ribosomes is the same in resting and growing cells. Thus these cells resemble 3T6 and translational control does not appear to be an important part of the change in protein synthetic rate with teh state of growth.
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