The Nucleocapsid Region of HIV-1 Gag Cooperates with the PTAP and LYPXnL Late Domains to Recruit the Cellular Machinery Necessary for Viral Budding

HIV-1 release is mediated through two motifs in the p6 region of Gag, PTAP and LYPXnL, which recruit cellular proteins Tsg101 and Alix, respectively. The Nucleocapsid region of Gag (NC), which binds the Bro1 domain of Alix, also plays an important role in HIV-1 release, but the underlying mechanism remains unclear. Here we show that the first 202 residues of the Bro1 domain (Broi) are sufficient to bind Gag. Broi interferes with HIV-1 release in an NC–dependent manner and arrests viral budding at the plasma membrane. Similar interrupted budding structures are seen following over-expression of a fragment containing Bro1 with the adjacent V domain (Bro1-V). Although only Bro1-V contains binding determinants for CHMP4, both Broi and Bro1-V inhibited release via both the PTAP/Tsg101 and the LYPXnL/Alix pathways, suggesting that they interfere with a key step in HIV-1 release. Remarkably, we found that over-expression of Bro1 rescued the release of HIV-1 lacking both L domains. This rescue required the N-terminal region of the NC domain in Gag and the CHMP4 binding site in Bro1. Interestingly, release defects due to mutations in NC that prevented Bro1 mediated rescue of virus egress were rescued by providing a link to the ESCRT machinery via Nedd4.2s over-expression. Our data support a model in which NC cooperates with PTAP in the recruitment of cellular proteins necessary for its L domain activity and binds the Bro1–CHMP4 complex required for LYPXnL–mediated budding

Effects of growth temperatures on the characteristics of n-GaN nanorods-graphene hybrid structures

The effects of different growth temperatures of n-GaN nanorods (NRs) on the material and electrical properties of n-GaN NRs-graphene hybrid device structures are being demonstrated for the first time. A high quality graphene transfer method was applied for transferring the graphene layer on Si (1 1 1) substrate and n-GaN NRs were synthesized on the graphene layer on Si using a metal organic chemical vapor deposition (MOCVD) process of high V/III ratio. No metal-catalyst or droplet seeds were formed when growing n-GaN NRs. The growth temperature of the n-GaN NRs was varied from 860 ??C to 900 ??C. Raman spectroscopy confirmed the prominent existence of an undamaged graphene layer in all of the highly-matched hybrid device structures under study. Improvement in the structural, crystalline and material properties was established from FE-SEM, XRD and PL studies for the hybrid structure where n-GaN NRs were grown at 890 ??C. The same hybrid structure also showed a ten-fold enhancement in photocurrent along with increased sensitivity and photoresponsivity. Therefore, it can be concluded that a suitable growth temperature of n-GaN NRs is the most important factor for the fabrication of high quality n-GaN NRs-graphene hybrid structures. © 2015 Elsevier B.V. All rights reservedclose0