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. 1998 Oct 27;95(22):12989–12994. doi: 10.1073/pnas.95.22.12989

Table 1.

Expression of β-gal by different SIN replicons

Replicon, noncytopathic/cytopathic μg of β-gal/106 cells*
SINrep19/lacZ, noncytopathic 1.4  ±  0.1
SINrep3/lacZ, cytopathic 40  ±  2.4
SINrep18 + DI/lacZ-neo, noncytopathic 31  ±  1.7
*

Amounts of β-gal were determined by comparison with concentration standards in enzymatic activity assays. Cell lysates were prepared following 2 days of puromycin selection (for noncytopathic replicons) or 18 h after infection at a moi of 10 (packaged cytopathic replicons). For the noncytopathic replicons, expression levels plateau after 2 days of selection; for the cytopathic replicons, 18 h precedes the onset of cytopathic effect although expression levels are only one-half maximal at this time. Standard BHK cells expressed undetectable β-gal activity. The sensitivity of this assay was ≈1 ng of purified enzyme. Values shown reflect the mean and SD for three replicate experiments. 

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