to observe the effects of polyoma virus dna on the expression of the herpes simplex virus ( hsv ) thymidine kinase ( tk ) gene early after transfer into tk-deficient mouse cells and the subsequent development of stable tk-positive transformants , we constructed a series of recombinant plasmids containing the herpes simplex virus tk gene joined with various segments of the polyoma virus genome and microinjected them into the nuclei or cytoplasm of ltk-a cells ( tk ( - ) , aprt ( - ) ) .
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nuclei
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cells