The pp24 phosphoprotein of Mason-Pfizer monkey virus contributes to viral genome packaging.
BACKGROUND
The Gag protein of Mason-Pfizer monkey virus, a betaretrovirus, contains a phosphoprotein that is cleaved into the Np24 protein and the phosphoprotein pp16/18 during virus maturation. Previous studies by Yasuda and Hunter (J. Virology. 1998. 72:4095-4103) have demonstrated that pp16/18 contains a viral late domain required for budding and that the Np24 protein plays a role during the virus life cycle since deletion of this N-terminal domain blocked virus replication. The function of the Np24 domain, however, is not known.


RESULTS
Here we identify a region of basic residues (KKPKR) within the Np24 domain that is highly conserved among the phosphoproteins of various betaretroviruses. We show that this KKPKR motif is required for virus replication yet dispensable for procapsid assembly, membrane targeting, budding and release, particle maturation, or viral glycoprotein packaging. Additional experiments indicated that deletion of this motif reduced viral RNA packaging 6-8 fold and affected the transient association of Gag with nuclear pores.


CONCLUSIONS
These results demonstrate that the Np24 domain plays an important role in RNA packaging and is in agreement with evidence that suggests that correct intracellular targeting of Gag to the nuclear compartment is an fundamental step in the retroviral life cycle.
Bohl
Christopher R
CR
School of Biological Sciences, The Nebraska Center for Virology, University of Nebraska, Lincoln, 68588, USA. cbohl1@hotmail.com
Brown
Shanna M
SM
Weldon
Robert A
RA
D036022:Capsid Proteins / Q000502:physiology; D042003:DNA Packaging; D019281:Dimerization; D015683:Gene Products, gag / Q000502:physiology; D016679:Genome, Viral; D016093:Mason-Pfizer monkey virus / Q000235:genetics / Q000502:physiology*; D010750:Phosphoproteins / Q000502:physiology*; D012367:RNA, Viral / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry / Q000502:physiology*; D019065:Virus Assembly; D014779:Virus Replication
D036022:Capsid Proteins; D015683:Gene Products, gag; D010750:Phosphoproteins; D012367:RNA, Viral; D014764:Viral Proteins