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Opposing mechanisms involving RNA and lipids regulate HIV-1 Gag membrane binding through the highly basic region of the matrix domain.

Abstract：

:Membrane binding of Gag, a crucial step in HIV-1 assembly, is facilitated by bipartite signals within the matrix (MA) domain: N-terminal myristoyl moiety and the highly basic region (HBR). We and others have shown that Gag interacts with a plasma-membrane-specific acidic phospholipid, phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)], via the HBR, and that this interaction is important for efficient membrane binding and plasma membrane targeting of Gag. Generally, in protein-PI(4,5)P(2) interactions, basic residues promote the interaction as docking sites for the acidic headgroup of the lipid. In this study, toward better understanding of the Gag-PI(4,5)P(2) interaction, we sought to determine the roles played by all of the basic residues in the HBR. We identified three basic residues promoting PI(4,5)P(2)-dependent Gag-membrane binding. Unexpectedly, two other HBR residues, Lys25 and Lys26, suppress membrane binding in the absence of PI(4,5)P(2) and prevent promiscuous intracellular localization of Gag. This inhibition of nonspecific membrane binding is likely through suppression of myristate-dependent hydrophobic interaction because mutating Lys25 and Lys26 enhances binding of Gag with neutral-charged liposomes. These residues were reported to bind RNA. Importantly, we found that RNA also negatively regulates Gag membrane binding. In the absence but not presence of PI(4,5)P(2), RNA bound to MA HBR abolishes Gag-liposome binding. Altogether, these data indicate that the HBR is unique among basic phosphoinositide-binding domains, because it integrates three regulatory components, PI(4,5)P(2), myristate, and RNA, to ensure plasma membrane specificity for particle assembly.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Chukkapalli V,Oh SJ,Ono A

doi

10.1073/pnas.0908661107

subject

Has Abstract

pub_date

2010-01-26 00:00:00

pages

1600-5

issue

eissn

0027-8424

issn

1091-6490

pii

0908661107

journal_volume

107

pub_type

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Opposing mechanisms involving RNA and lipids regulate HIV-1 Gag membrane binding through the highly basic region of the matrix domain.