Fig. 4.

Regression of an RPA-covered replication fork. (A) Experimental scheme. RPA binds to the 114-nt gap on the lagging strand template of the replication fork. Fork regression results in the transfer of the ³²P label (asterisk) from the replication fork to the 0.5-kb linear duplex product. (B) Binding of RPA to the replication fork was verified by agarose gel-shift analysis. (C) Analysis of fork regression by agarose gel electrophoresis. FANCM and the replication-fork substrate were incubated for the indicated time periods without (lane 4) and with (lane 5) preincubation of the replication fork with RPA. As a control, the substrate was incubated without FANCM in the absence (lanes 1 and 2) or presence (lane 3) of RPA. Asterisks indicate background of labeled gapped DNA (*) and labeled linear DNA (**).