DNA replication can be restored by adding purified Polɛ back to the
depleted extracts. (A) Purification of
Xenopus Polɛ from egg extracts. An elution profile of
DNA polymerase activity from Mono Q column (Top),
immunoblots with Polɛ p60 or Polα p70 antibodies
(Middle), and a silver-stained protein gel
(Bottom) of the corresponding fractions are shown.
Arrowheads indicate the positions of the catalytic subunit (p260) and
p60 of Polɛ, respectively. (B) Restoration
of DNA replication by the addition of purified Polɛ back to
Polɛ-depleted extracts. The products from the reactions (70-min
incubation) with mock- or Polɛ-depleted extracts (14 μl each)
supplemented with 1 μl each of control buffer or each Mono Q fraction
containing Polɛ (fraction 28 in A), Polα (fraction
23 in A), or free p60 (fraction 21 in A)
were analyzed as in Fig. 2C. The position of the origin
for gel electrophoresis (ori) is indicated on the right. The sizes of
marker DNA are on the left.