Protein IX, a minor component of the human adenovirus capsid, is essential for the packaging of full length genomes.

Human adenovirus type 5 (Ad5) contains a 36‐kb double‐stranded DNA molecule in an icosahedral capsid. Attempts to construct Ad5 insertion mutants containing DNA of more than about 105% of the genome size resulted in viral progeny in which deletions had occurred suggesting the existence of severe constraints on the size of packageable DNA molecules. To partially circumvent these constraints we used an adenovirus vector, Ad5dlE1,3, with deletions …