Conserved features in papillomavirus and polyomavirus capsids

Area of Science:

• Structural virology
• Molecular biology
• Biophysics

Background:

• Papovavirus family viruses, including papillomaviruses and polyomaviruses, assemble capsids from 72 pentameric capsomeres on a T=7 icosahedral lattice.
• Previous studies indicated differing lattice handedness (left-handed for CRPV, right-handed for others) within this family.
• Papillomavirus capsid structures, like those of BPV-1 and HPV-1, exhibit star-shaped capsomeres and can exist in open or closed forms.

Purpose of the Study:

• To investigate the capsid structure and lattice handedness of Cottontail Rabbit Papillomavirus (CRPV).
• To compare the structural features of papillomaviruses with those of polyomaviruses.
• To elucidate the conserved structural elements within the Papovaviridae family.

Main Methods:

• Cryoelectron microscopy and image reconstruction were employed to determine the CRPV capsid structure.
• Comparative analysis of structural data from CRPV, BPV-1, HPV-1, SV40, and murine polyomavirus.
• Examination of capsomere morphology, lattice arrangement, and intercapsomere interactions.

Main Results:

• The CRPV capsid structure was determined to be T=7 dextro (right-handed), consistent with other examined papillomaviruses.
• Open CRPV capsids showed an increased radius compared to closed forms, with star-shaped capsomeres.
• Papillomavirus capsomeres interact similarly to polyomaviruses, despite differences in size and morphology.

Conclusions:

• Papovavirus capsids exhibit a conserved T=7 dextro structure, characterized by 72 pentameric capsomeres.
• Structural conservation persists despite significant variations in viral capsid protein sequences.
• Stable intra-capsomere contacts and flexible inter-capsomere linkages likely drive the conserved capsid architecture.