Fig. 1.

A: Immunodetection of DNA primase subunits p49 and p58 by Western blot analysis in different fractions during the purification of the DNA synthesome. The fractions include homogenate (H), low to high speed cytosolic supernatants 1–3 (S1–3), nuclear extract (NE), and the upper 70% (S4) and the lower 30% (P4) of the soluble protein derived from a 16 h ultracentrifugation of the combined NE/S3 [Lin et al., 1997]. B: DNA primase activity in different fractions of the synthesome was examined using a primer extension assay (Materials and Methods Section). The reaction was performed at 37°C for 1 h in 25 μl mixtures contained 60 nmol poly(dT), 10 μg of each different fraction, 500 μM ATP, 100 μM (³H)-dATP and 0.5 U of the Klenow fragment of E. coli DNA polymerase I. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]