Sizing nascent
SV40 DNA chains radiolabeled in the DNA moiety and crosslinked to
RPA subunits. (A) Photolabeled RPA was isolated
from the pulse-labeled replication mixture without DNase I treatment,
as detailed in Figure 1 and Materials and Methods. Precipitates of pre-clearing (lane
1) and IP of RPA under native conditions (lane 2) were resolved
by SDS–PAGE. (B) The Rpa1 and Rpa2 bands
were excised from the indicated gel sections. The photolabeled proteins
were extracted and treated with proteinase K. After phenol extraction,
the released nascent DNA was separated by electrophoresis on 15% TBU
gel (Novex). (C) Densitometric profiles of (B),
lane 1 (red) and lane 2 (cyan). Peak values and half peak values
marking distributions borders are indicated by respective full or
dashed vertical lines in corresponding color. kDa, protein size
markers; nt, nucleotide size markers; Prcl, pre-clearing immunoprecipitate;
Ipc, specific immunoprecipitate.