1. * RSV Core Assembly: It’s All About Nucleation
Title page
* RSV Core Assembly: It’s All About Nucleation
Carmen Butan, Giovanni Cardone, Naiqian Cheng,
Bernard Heymann, Paul Keller, Dennis Winkler
Laboratory of Structural Biology, NIAMS-NIH
Parvez Lokhandwala, John Purdy, Rebecca Craven
Pennsylvania State University College of Medicine

2. Retroviruses are highly variable in their capsid architecture, both for a given retrovirus and between different retroviruses.
With HIV, the predominant capsid morphology is biconical; with Rous sarcoma virus, it is irregular polyhedra. Cylindrical tubes with and without end-caps are also produced. .

3. Butan et al. (2008) J. Mol. Biol., 376, 1168-81
Cryo-electron tomogram of Rous sarcoma virus
Butan et al. (2008) J. Mol. Biol., 376,

4. Angular, curved and miscellaneous cores

6. Virions with angular cores have many spikes:
Virions with tubular cores have few spikes

7. In retroviruses, the capsid assembles de novo
inside the provirion, post-budding
Not all of the capsid protein assembles:
> 50% remains unassembled (Prevelige et al; Fuller et al)

8. Angular cores correlate with high CA assembly efficiencies:
Tubular cores correlate with low CA assembly efficiencies
Measure #Gag
( total # CA) from
virion diameter

9. Observations The range of polymorphic variation is very large
tubular cores and many “curved”cores - including biconical RSV
cores - fail to package RNP
Hypothesis: a viable core is one that is closed and has successfully packaged the genome(s) and the polymerase

10. Observations The range of polymorphic variation is very large
tubular cores and many “curved”cores - including biconical RSV
cores - fail to package RNP
Hypothesis: a viable core is one that is closed and has successfully packaged the genome(s) and the polymerase
Inference: Initiation is key to capsid assembly

11. Critical concentrations for assembly
conc’n of protein subunits in capsids
Total conc’n of protein subunits

12. Nucleation of angular nucleocapsid assembly : a model