FIG. 4.

TBP depletion of S100 extracts stimulates their activity in SV40 DNA replication in vitro. (A) A 100-μg aliquot of S100 extract from 293 cells (lane 2), TBP-depleted S100 extract (lane 3), or mock depleted S100 extract (lane 4) was analyzed by SDS-PAGE (10% gel) and immunoblotting with anti-TBP monoclonal antibody 4C8. As a marker, 0.25 μg of thrombin-cleaved GST-TBP was analyzed in parallel (lane 1). The upper band contains some uncleaved fusion protein. (B) SV40 DNA replication in vitro was assayed by using the indicated amounts of protein from TBP-depleted S100 extract or mock-depleted S100 extract. Replication activity was quantitated by measuring the incorporation of radiolabeled nucleotides into DNA.