FIG. 4.

Immunolocalization of FEN1 to mitochondria. (A) Representative images of colocalization of FEN1 and mitochondrion-specific heat shock protein (mtHSP70) in HeLa cells. Fixed HeLa cells were costained with anti-FEN1 (α-FEN1) and anti-mtHsp70 (α-mtHSP70) antibodies. In the merged views, the yellow spots indicate colocalization of FEN1 and mtHsp70. The boxed area in each frame is shown magnified in the upper right; this better illustrates the extranuclear staining of FEN1 and mtHSP70. (B) Representative images of the localization of FEN1 and mtHsp70 in HeLa cells expressing wild-type (WT) and Y83H mutant forms of the nuclease.