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Interaction of the 89K murine cytomegalovirus immediate-early protein with core histones
K Münch1, G M Keil, M Messerle
1Federal Research Center for Virus Diseases of Animals, Tübingen, Federal Republic of Germany.
Abstract:
The conditions that permit the interaction of immediate-early proteins of murine cytomegalovirus (MCMV) with DNA were studied. Chromatography of extracts from infected cells on MCMV DNA cellulose and calf thymus DNA cellulose showed that pp89, the regulatory major immediate-early protein, interacts with DNA and dissociates at salt concentrations between 0.3 and 0.6 M NaCl. pp76, a cleavage product of pp89, and additional minor ie 1 proteins eluted already at low ionic strength. Cellular DNA-binding factors were required for association of pp89 with DNA. These factors were identified as core histones. Chromatography of IE proteins on histone-Sepharose in the absence of DNA revealed a high-binding affinity that was resistant to 2 M NaCl. These results suggest that pp89 has no direct DNA-binding activity. A role for an amino acid sequence homology in the N-terminal region of pp89 with histone H2B in the pp89-histone-DNA interaction is discussed.
Insights
Murine cytomegalovirus (MCMV) immediate-early protein pp89 requires cellular histones for DNA interaction, suggesting it lacks direct DNA-binding activity. This interaction may involve N-terminal sequence homology with histone H2B.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Murine cytomegalovirus (MCMV) immediate-early (IE) proteins play crucial roles in viral replication.
- Understanding the DNA-binding properties of MCMV IE proteins is essential for elucidating viral gene regulation.
Purpose of the Study:
- To investigate the conditions and factors involved in the interaction of MCMV immediate-early proteins with DNA.
- To determine whether MCMV IE proteins possess intrinsic DNA-binding capabilities.
Main Methods:
- Chromatography of infected cell extracts on MCMV and calf thymus DNA cellulose.
- Analysis of protein elution profiles at varying salt concentrations.
- Affinity chromatography of IE proteins on histone-Sepharose.
Main Results:
- The major immediate-early protein pp89 interacts with DNA, dissociating between 0.3-0.6 M NaCl.
- pp76 and minor IE1 proteins showed weak DNA binding at low ionic strength.
- Cellular core histones were identified as essential factors for pp89-DNA association.
- pp89 exhibited high-affinity binding to histones, resistant to 2 M NaCl, indicating no direct DNA-binding activity.
Conclusions:
- MCMV pp89 does not directly bind DNA; its association requires cellular core histones.
- The interaction between pp89 and DNA is likely mediated by histone binding.
- Sequence homology between pp89's N-terminus and histone H2B may facilitate this interaction.