Bipartite structure and functional independence of adenovirus type 5 packaging elements

Area of Science:

• Molecular Virology
• Genetics

Background:

• Adenovirus type 5 DNA packaging involves interactions between packaging factors and a cis-acting packaging domain.
• This domain contains functional elements (A repeats), with elements I, II, V, and VI being crucial.
• Previous studies indicated packaging sensitivity to spatial arrangements of these A repeats.

Purpose of the Study:

• To investigate the role of spatial constraints between A repeats in adenovirus DNA packaging.
• To identify critical sequences and structural motifs within the adenovirus packaging domain.

Main Methods:

• Site-directed mutagenesis of linker regions between specific A repeats (I-II and V-VI).
• Analysis of viral packaging efficiency in vivo.
• Selection of revertants from packaging-deficient adenovirus.
• Identification of minimal packaging domain segments.

Main Results:

• Previously unrecognized sequences critical for DNA encapsidation were identified.
• A more complex, bipartite consensus motif for adenovirus packaging elements was proposed.
• Changes in spacing within the bipartite motif, rather than between A repeats, compromised DNA encapsidation.
• Multimerization of packaging repeats was sufficient for packaging competence.
• Minimally sized segments conferring packaging activity were identified.

Conclusions:

• The adenovirus packaging domain has a bipartite structure critical for DNA encapsidation.
• Spatial constraints within this bipartite motif are more important than spacing between individual A repeats.
• Trans-acting factors likely play a role in adenovirus DNA packaging, as suggested by revertant and mutant analyses.