Selective Loss of Poly(ADP-ribose) and the 85-kDa Fragment of Poly(ADP-ribose) Polymerase in Nucleoli during Alkylation-induced Apoptosis of HeLa Cells

• Published in: The Journal of biological chemistry 1999-11, Vol.274 (45), p.32122-32126
• Main Authors: Alvarez-Gonzalez, Rafael, Spring, Herbert, Müller, Marcus, Bürkle, Alexander
• Format: Article
• Language: English
• Subjects: Alkylation; Apoptosis; Cell Nucleolus - metabolism; DNA Damage; HeLa Cells; Humans; Molecular Weight; Peptide Fragments - metabolism; Poly Adenosine Diphosphate Ribose - metabolism; poly(ADP-ribose) polymerase; Poly(ADP-ribose) Polymerases - metabolism; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.45.32122

Alkylation treatment of HeLa cells results in the rapid induction of apoptosis as revealed by DNA laddering and cleavage of poly(ADP-ribose) polymerase (PARP) into the 29-and 85-kDa fragments (Kumari S. R., Mendoza-Alvarez, H. & Alvarez-Gonzalez, R. (1998)Cancer Res. 58, 5075–5078). Here, we performed a time-course analysis of (i) poly(ADP-ribose) synthesis and degradation as well as (ii) the subnuclear localization of PARP and its fragments by using confocal laser scanning immunofluorescence microscopy. PARP was activated within 15 min post-treatment, as revealed by nuclear immunostaining with antibody 10H (recognizing poly(ADP-ribose)). This was followed by a late, time-dependent, progressive decline of 10H signals that coincide with the time of PARP cleavage. Strikingly, nucleolar immunostaining with antibodies 10H and C-II-10 (recognizing the 85-kDa PARP fragment) was lost by 15 min post-treatment, whereas F-I-23 signals (recognizing the 29-kDa fragment) persisted. We hypothesize that the 85-kDa PARP fragment is translocated, along with covalently bound poly(ADP-ribose), from nucleoli to the nucleoplasm, whereas the 29-kDa fragment is retained, because it binds to DNA strand breaks. Our data (i) provide a link between the known time-dependent bifunctional role of PARP in apoptosis and the subcellular localization of PARP fragments and also (ii) add to the evidence for early proteolytic changes in nucleoli during apoptosis.