Fig. 1. Subnuclear distribution of endogenous PARP-2 in human and mouse cells. (A) Confocal sections showing the simultaneous immunodetection of PARP-2 and PARP-1 in HeLa cells fixed with 2% formaldehyde (FA, top), or HeLa cells (middle) and MEFs (bottom) fixed with 1% formaldehyde/0.1% Triton X-100. The morphology of the nucleus is illustrated by differential interference contrast (DIC) images. Merged images of stained PARP-2 and either stained PARP-1 or the DIC image are shown. Inset shows a 2x magnification of the area indicated by the square. To improve the resolution of final images, only the nuclei are displayed as no specific signal above background was detected in the cytoplasm. (B) Cellular fractionation of HeLa cells. 15 µg of each cellular fraction were analyzed by western blotting with antibodies against B23 (bottom), PARP-2 (middle) and PARP-1 (top). WCE, whole cell extract; Cyto, cytoplasmic fraction; Nu, nuclear fraction; Np, nucleoplasmic fraction; No, nucleolar fraction. (C) Confocal sections showing the simultaneous immunodetection of PARP-2 and B23 in HeLa cells (top) or MEFs (bottom) fixed with 1% formaldehyde/0.1% Triton X-100. Merged images of stained PARP-2 and either stained B23 or the DIC image are shown. Bar, 10 µm.