Comparison of various HeLa extracts in the integration assay. (a) The reaction was carried out with 30 μg of uninfected nuclear extract (lane N), uninfected cytoplasmic extract (lane C), or adenovirus-infected cytoplasmic extract (lane Ad). (b) Increasing amounts of crude HMG extract (0, 0.1, 0.5, and 1 μg) was added to the integration reaction containing cytoplasmic HeLa extract.