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Biochemistry. 1994 Jun 14;33(23):7099-106.

Dual function for poly(ADP-ribose) synthesis in response to DNA strand breakage.

Author information

1
Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Hertfordshire, U.K.

Abstract

Soluble extracts of human cells repair gamma-ray-induced single-strand breaks in DNA. Accompanying NAD-dependent automodification of poly(ADP-ribose) polymerase is required for effective DNA rejoining. The kinetics of poly(ADP-ribose) synthesis by this polymerase, and subsequent polymer degradation by poly(ADP-ribose) glycohydrolase, have been compared with the rate of DNA repair. The results agree with previous in vivo data. In response to addition of gamma-irradiated plasmid DNA, rapid and heavy automodification of poly(ADP-ribose) polymerase occurred in NAD-containing human cell extracts. After 2 min at 30 degrees C, when very little DNA rejoining had yet occurred, synthesis of long polymers essentially ceased, although only a minor fraction of the NAD had been consumed. Poly(ADP-ribose) chains were then reduced to oligomer size by poly(ADP-ribose) glycohydrolase. These short chains were present for longer times and were sufficient to permit DNA repair. Thus, most but not all poly(ADP-ribose) synthesis could be suppressed without marked inhibition of DNA repair, and prolonged occurrence of long poly(ADP-ribose) chains in consequence to glycohydrolase inhibition did not improve DNA repair. The temporary presence of short poly(ADP-ribose) chains on poly(ADP-ribose) polymerase avoids inhibition of excision-repair by that protein, but the initial very transient formation of long and branched chains of poly(ADP-ribose) in response to DNA damage apparently serves an entirely different purpose. Local poly(ADP-ribose) synthesis in the vicinity of a DNA strand interruption causes negative charge repulsion, and this may function to prevent accidental homologous recombination events within tandem repeat DNA sequences.

PMID:
8003475
DOI:
10.1021/bi00189a012
[Indexed for MEDLINE]

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