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Polyoma virus minichromosomes: poly ADP-ribosylation of associated chromatin proteins
Abstract:
The host nuclear enzyme poly(ADP-ribose) polymerase has been shown to be associated with the replicative intermediate and mature forms of polyoma virus minichromosomes. Minichromosome-associated histones H2A and H2B as well as several nonhistone proteins were poly ADP-ribosylated by endogenous poly(ADP-ribose) polymerase. In addition, minichromosome fractions catalyzed the formation in vitro of dimers of endogenous histone H1 linked by poly(ADP-ribose). Poly ADP-ribosylated polyoma virus minichromosome chromatin labeled in vivo with [3H]thymidine could be retained and eluted from anti-poly(ADP-ribose) immunoglobulin G-Sepharose. Pulse-labeled replicative intermediate minichromosomes were retained better on the antibody columns than were mature minichromosomes labeled for 2.5 h. The possible role of poly ADP-ribosylation of viral nucleosomes during polyoma replication or transcription is discussed.
Insights
Poly(ADP-ribose) polymerase modifies polyoma virus minichromosomes, including histones and nonhistone proteins. This modification aids in retaining viral chromatin, suggesting a role in polyoma replication.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- The host nuclear enzyme poly(ADP-ribose) polymerase (PARP) is involved in DNA repair and chromatin remodeling.
- Polyoma virus minichromosomes are viral DNA-protein complexes essential for viral replication and transcription.
Purpose of the Study:
- To investigate the association of poly(ADP-ribose) polymerase with polyoma virus minichromosomes.
- To determine the role of poly ADP-ribosylation in viral chromatin structure and function during polyoma replication.
Main Methods:
- Enzymatic assays to detect poly ADP-ribosylation of minichromosome-associated proteins.
- Chromatographic separation using anti-poly(ADP-ribose) immunoglobulin G-Sepharose to isolate modified viral chromatin.
- In vivo labeling of viral chromatin with [3H]thymidine to assess retention and elution characteristics.
Main Results:
- Poly(ADP-ribose) polymerase was found associated with both replicative intermediate and mature polyoma virus minichromosomes.
- Histones H2A, H2B, and several nonhistone proteins were poly ADP-ribosylated by endogenous PARP.
- Minichromosome fractions catalyzed in vitro the formation of histone H1 dimers linked by poly(ADP-ribose).
- Poly ADP-ribosylated viral chromatin could be retained and eluted using anti-poly(ADP-ribose) affinity chromatography.
- Replicative intermediate minichromosomes showed higher retention on antibody columns compared to mature minichromosomes.
Conclusions:
- Poly ADP-ribosylation modifies key components of polyoma virus minichromosomes, including histones and nonhistone proteins.
- The modification by poly(ADP-ribose) polymerase appears to play a role in the structural organization or processing of viral chromatin.
- Further investigation is warranted to elucidate the specific functions of poly ADP-ribosylation in polyoma virus replication and transcription.