Myristoylation drives dimerization of matrix protein from mouse mammary tumor virus

Abstract

BackgroundMyristoylation of the matrix (MA) domain mediates the transport and binding of Gag polyproteins to the plasma membrane (PM) and is required for the assembly of most retroviruses. In betaretroviruses, which assemble immature particles in the cytoplasm, myristoylation is dispensable for assembly but is crucial for particle transport to the PM. Oligomerization of HIV-1 MA stimulates the transition of the myristoyl group from a sequestered to an exposed conformation, which is more accessible for membrane binding. However, for other retroviruses, the effect of MA oligomerization on myristoyl group exposure has not been thoroughly investigated.ResultsHere, we demonstrate that MA from the betaretrovirus mouse mammary tumor virus (MMTV) forms dimers in solution and that this process is stimulated by its myristoylation. The crystal structure of N-myristoylated MMTV MA, determined at 1.57 Å resolution, revealed that the myristoyl groups are buried in a hydrophobic pocket at the dimer interface and contribute to dimer formation. Interestingly, the myristoyl groups in the dimer are mutually swapped to achieve energetically stable binding, as documented by molecular dynamics modeling. Mutations within the myristoyl binding site resulted in reduced MA dimerization and extracellular particle release.ConclusionsBased on our experimental, structural, and computational data, we propose a model for dimerization of MMTV MA in which myristoyl groups stimulate the interaction between MA molecules. Moreover, dimer-forming MA molecules adopt a sequestered conformation with their myristoyl groups entirely buried within the interaction interface. Although this differs from the current model proposed for lentiviruses, in which oligomerization of MA triggers exposure of myristoyl group, it appears convenient for intracellular assembly, which involves no apparent membrane interaction and allows the myristoyl group to be sequestered during oligomerization.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-015-0235-8) contains supplementary material, which is available to authorized users.

High-Throughput Sequencing is a Crucial Tool to Investigate the Contribution of Human Endogenous Retroviruses (HERVs) to Human Biology and Development

“…A third interesting tool is RetroTector, a software developed for the automated recognition of the best-preserved proviral sequences in the genome of vertebrates [ 45 , 46 ]. The HERV recognition process through RetroTector led to a related study that analyzed the human genome assembly GRCh 37/hg19, identifying, characterizing and classifying a total of 3173 HERV sequences [ 3 ]. The classification work, based on a multiple approach, split the HERV proviruses into 39 well-supported phylogenetic groups, belonging to the retroviral classes I (Gamma- and Epsilon-like), II (Beta-like), and III (Spuma-like) [ 3 ].…”

“…The HERV recognition process through RetroTector led to a related study that analyzed the human genome assembly GRCh 37/hg19, identifying, characterizing and classifying a total of 3173 HERV sequences [ 3 ]. The classification work, based on a multiple approach, split the HERV proviruses into 39 well-supported phylogenetic groups, belonging to the retroviral classes I (Gamma- and Epsilon-like), II (Beta-like), and III (Spuma-like) [ 3 ]. Interestingly, an additional 31 noncanonical HERV groups were identified, revealing a high degree of mosaicism [ 3 ].…”

“…The classification work, based on a multiple approach, split the HERV proviruses into 39 well-supported phylogenetic groups, belonging to the retroviral classes I (Gamma- and Epsilon-like), II (Beta-like), and III (Spuma-like) [ 3 ]. Interestingly, an additional 31 noncanonical HERV groups were identified, revealing a high degree of mosaicism [ 3 ]. RetroTector can also predict the sequence of the retroviral genes and a multitude of other retroviral features, like the Primer Binding Site (PBS) or the Poly Purine Tract (PPT), as well as the putative protein products.…”

“…RetroTector can also predict the sequence of the retroviral genes and a multitude of other retroviral features, like the Primer Binding Site (PBS) or the Poly Purine Tract (PPT), as well as the putative protein products. By contrast, it is unable to detect solo LTRs [ 3 ].…”

“…Human Endogenous Retroviruses (HERVs) are repetitive elements derived from infection by ancient retroviruses, now extinct, that integrated within the genome of primate germ line cells and have been transmitted as proviruses through the offspring [ 1 ]. These sequences currently constitute a significant portion (about 8%) of human DNA [ 2 , 3 ]. The majority of HERVs have lost their replication and expression activities, mostly due to deletions and recombination events, or for the accumulation of several mutations that inactivated them, while some HERVs have maintained the classical proviral structure—including the main genes flanked by two Long Terminal Repeats (LTRs)—and have, thus, the potential for transcriptional activity [ 1 , 4 ].…”