Abstract
The cellular role of breast carcinoma-associated protein (BCA3), also known as A-kinase-interacting protein 1 (AKIP-1), is not fully understood. Recently, we reported that full-length, but not C-terminally truncated, BCA3 is incorporated into virions of Mason-Pfizer monkey virus, and that BCA3 enhances HIV-1 protease-induced apoptosis. In the present study, we report that BCA3 is associated with purified and subtilisin-treated HIV particles. Using a combination of immune-based methods and confocal microscopy, we show that the C-terminus of BCA3 is required for packaging into HIV-1 particles. However, we were unable to identify an HIV-1 binding domain for BCA3, and we did not observe any effect of incorporated BCA3 on HIV-1 infectivity. Interestingly, the BCA3 C-terminus was previously identified as a binding site for the catalytic subunit of protein kinase A (PKAc), a cellular protein that is specifically packaged into HIV-1 particles. Based on our analysis of PKAc–BCA3 interactions, we suggest that BCA3 incorporation into HIV-1 particles is mediated by its ability to interact with PKAc.
Highlights
HIV-1 has a limited genome, which leverages alternative splicing to produce nine products: three polyprotein precursors comprising structural (Gag), enzymatic (Pol) and envelope (Env) proteins, and the six accessory proteins Tat, Rev, Vif, Vpr, Nef and Vpu
We found that Breast cancer-associated protein 3 (BCA3) facilitates HIV-1 PR-mediated apoptosis [12]
Similar to its behavior with Mason-Pfizer monkey virus (M-PMV), BCA3 is packaged into HIV-1 particles, and the BCA3 C-terminus is responsible for this incorporation
Summary
HIV-1 has a limited genome, which leverages alternative splicing to produce nine products: three polyprotein precursors comprising structural (Gag), enzymatic (Pol) and envelope (Env) proteins, and the six accessory proteins Tat, Rev, Vif, Vpr, Nef and Vpu. Many cellular proteins have been found inside or on the surface of the virus. These cellular proteins are incorporated into HIV particles during assembly and budding, and they often play important roles during the early phase of viral infection. Some proteins become incorporated into the virion due to their proximity during assembly/budding or due to their ability to bind a “real” HIV-1 interaction partner. The catalytic subunit of cAMP-dependent protein kinase A (PKAc) is among the cellular proteins packaged within highly purified HIV-1 particles [1]. Some evidence indicates that HIV-1-associated active PKAc plays an important role during post-entry events comprising the early stage of reverse transcription [2]
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