Matrix domain modulates HIV-1 Gag's nucleic acid chaperone activity via inositol phosphate binding.
Retroviruses replicate by reverse transcribing their single-stranded RNA genomes into double-stranded DNA using specific cellular tRNAs to prime cDNA synthesis. In HIV-1, human tRNA(3)(Lys) serves as the primer and is packaged into virions during assembly. The viral Gag protein is believed to chaperone tRNA(3)(Lys) placement onto the genomic RNA primer binding site; however, the timing and possible regulation of this event are currently unknown. Composed of the matrix (MA), capsid (CA), nucleocapsid (NC), and p6 domains, the multifunctional HIV-1 Gag polyprotein orchestrates the highly coordinated process of virion assembly, but the contribution of these domains to tRNA(3)(Lys) annealing is unclear. Here, we show that NC is absolutely essential for annealing and that the MA domain inhibits Gag's tRNA annealing capability. During assembly, MA specifically interacts with inositol phosphate (IP)-containing lipids in the plasma membrane (PM). Surprisingly, we find that IPs stimulate Gag-facilitated tRNA annealing but do not stimulate annealing in Gag variants lacking the MA domain or containing point mutations involved in PM binding. Moreover, we find that IPs prevent MA from binding to nucleic acids but have little effect on NC or Gag. We propose that Gag binds to RNA either with both NC and MA domains or with NC alone and that MA-IP interactions alter Gag's binding mode. We propose that MA's interactions with the PM trigger the switch between these two binding modes and stimulate Gag's chaperone function, which may be important for the regulation of events such as tRNA primer annealing.
Department of Chemistry and Biochemistry, Center for Retroviral Research, and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA.
Christopher P
CP
Jones
Siddhartha A K
SA
Datta
Alan
A
Rein
Ioulia
I
Rouzina
Karin
K
Musier-Forsyth
D001483:Base Sequence; D015488:HIV Antigens / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D015488:HIV Antigens; D007295:Inositol Phosphates; D018832:Molecular Chaperones; D019590:Nucleocapsid Proteins; D012346:RNA, Transfer, Amino Acyl; D012367:RNA, Viral; D054301:gag Gene Products, Human Immunodeficiency Virus; C054858:p17 protein, Human Immunodeficiency Virus Type 1