The immunodetection of pADPr in Drosophila tissues: immunostaining of thick sections; immuno-EM

Poly(ADP)ribose (pADPr) modification is known to regulate the state of DNA condensation in the cell nucleus. Under normal conditions, pADPr is extremely unstable due to the enzymatic activity of pADPr glycohydrolase (PARG). We studied the salivary glands of PARG-deficient Drosophila larvae at both the fluorescence and electron microscope levels by immunolabeling of pADPr on cryosections. This approach proved very successful in preserving the antigenicity of pADPr as well as other antigens. pADPr concentrates in areas intercalating to heterochromatin as well as two types of nuclear granules that were subsequently shown to represent ectopic Cajal bodies.