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An Assay for Quantifying Protein-RNA Binding in Bacteria

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Intact ribonucleic acid from defective particles of bacteriophage R17.

J E Argetsinger¹, G N Gussin

¹Biological Laboratories, Harvard University Cambridge, Massachusetts, USA.

Journal of Molecular Biology

|September 23, 2009

Summary

Amber mutants of bacteriophage R17 produce defective, non-infectious particles. Studies reveal that RNase I degrades RNA during purification, not during phage growth, impacting particle infectivity and density.

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Area of Science:

Molecular Biology
Virology
Bacteriology

Background:

Amber mutants of bacteriophage R17 (class A) produce defective, non-infectious particles when grown in non-permissive hosts.
Previous studies indicated these defective particles are non-infectious.

Purpose of the Study:

To investigate the characteristics of defective bacteriophage-like particles produced by wild-type R17 and class A mutants.
To determine the role of RNase I in RNA degradation within these defective particles.
To explore the function of the R17 A protein.

Main Methods:

Growth of wild-type R17 and four class A mutants on Escherichia coli strains AB301 (non-permissive) and RNase(-)10 (RNase I-deficient).
Analysis of particle density using cesium chloride gradients.
Assessment of RNA integrity and infectivity via nuclease susceptibility assays.

Main Results:

Defective particles grown on AB301 contained degraded RNA and were less dense than wild-type phage.
Particles grown on RNase(-)10 contained intact, infectious RNA and had normal density but remained non-infectious.
RNA in purified defective particles from RNase(-)10 was susceptible to nucleases, unlike RNA in wild-type phage.

Conclusions:

Degraded RNA in R17 defective particles is a result of RNase I activity during purification, not during phage growth.
RNase I plays a critical role in RNA integrity and potentially phage infectivity.
The findings provide insights into the function of the R17 A protein in the context of particle assembly and stability.