Work

A Dimer as a Building Block in Assembling RNA

Year: 2000

Type: article

Abstract: Six RNA (pRNA) molecules form a hexamer, via hand-in-hand interaction, to gear bacterial virus phi29 DNA translocation machinery. Here we report the pathway and the conditions for the hexamer formation. Stable pRNA dimers and trimers were assembled in solution, isolated from native gels, and separated by sedimentation, providing a model system for the study of RNA dimers and trimers in a protein-free environment. Cryo-atomic force microscopy revealed that monomers displayed a ✓ outline, dimers exhibited an elongated shape, and trimers formed a triangle. Dimerization of pRNA was promoted by a variety of cations including spermidine, whereas procapsid binding and DNA packaging required specific divalent cations, including Mg 2+ , Ca 2+ , and Mn 2+ . Both the tandem and fused pRNA dimers with complementary loops designed to form even-numbered rings were active in DNA packaging, whereas those without complementary loops were inactive. We conclude that dimers are the building blocks of the hexamer, and the pathway of building a hexamer is: dimer → tetramer → hexamer. The Hill coefficient of 2.5 suggests that there are three binding sites with cooperative binding on the surface of the procapsid. The two interacting loops played a key role in recruiting the incoming dimer, whereas the procapsid served as the foundation for hexamer assembly.

Source: Journal of Biological Chemistry

DOI: 10.1074/jbc.m909662199

Authors: Chaoping Chen, Sitong Sheng, Zhifeng Shao, Peixuan Guo

Institutions: Purdue University West Lafayette, University of Virginia

Language: English

Topic: RNA and protein synthesis mechanisms

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: hybrid

Estimated APC paid: $3,430

Funders: National Institute of General Medical Sciences, National Center for Research Resources