Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
EMBO J. 2020 Oct 15;39(20):e104870. doi: 10.15252/embj.2020104870. Epub 2020 Sep 8.
While the microtubule end-binding protein, EB1 facilitates early stages of HIV-1 infection, how it does so remains unclear. Here, we show that beyond its effects on microtubule acetylation, EB1 also indirectly contributes to infection by delivering the plus-end tracking protein (+TIP), cytoplasmic linker protein 170 (CLIP170) to the cell periphery. CLIP170 bound to intact HIV-1 cores or in vitro assembled capsid-nucleocapsid complexes, while EB1 did not. Moreover, unlike EB1 and several other +TIPs, CLIP170 enhanced infection independently of effects on microtubule acetylation. Capsid mutants and imaging revealed that CLIP170 bound HIV-1 cores in a manner distinct from currently known capsid cofactors, influenced by pentamer composition or curvature. Structural analyses revealed an EB-like +TIP-binding motif within the capsid major homology region (MHR) that binds SxIP motifs found in several +TIPs, and variability across this MHR sequence correlated with the extent to which different retroviruses engage CLIP170 to facilitate infection. Our findings provide mechanistic insights into the complex roles of +TIPs in mediating early stages of retroviral infection, and reveal divergent capsid-based EB1 mimicry across retroviral species.
微管末端结合蛋白 EB1 有助于 HIV-1 感染的早期阶段，但具体机制尚不清楚。在这里，我们发现 EB1 除了对微管乙酰化的影响外，还通过将 +TIP（细胞质连接蛋白 170，CLIP170）递送至细胞外周间接促进感染。CLIP170 与完整的 HIV-1 核心或体外组装的衣壳-核衣壳复合物结合，而 EB1 则没有。此外，与 EB1 和其他几种 +TIP 不同，CLIP170 能够独立于微管乙酰化的影响增强感染。衣壳突变体和成像显示，CLIP170 以不同于目前已知衣壳共因子的方式结合 HIV-1 核心，受五聚体组成或曲率的影响。结构分析显示，衣壳主要同源区（MHR）内存在类似于 EB 的 +TIP 结合基序，可结合几种 +TIP 中的 SxIP 基序，并且该 MHR 序列的变异性与不同逆转录病毒与 CLIP170 结合以促进感染的程度相关。我们的研究结果为 +TIP 在介导逆转录病毒感染早期阶段的复杂作用提供了机制见解，并揭示了不同逆转录病毒物种之间衣壳基 EB1 模拟的差异。
