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A genome-wide CRISPR-Cas9 activation screen identified FBXO34 as a host factor whose activation promotes latent HIV-1 reactivation, and AP-MS/co-IP identified hnRNP U as an FBXO34-interacting substrate whose ubiquitination and degradation FBXO34 promotes.
"A genome-wide **CRISPR-Cas9 activation** screen in a latent HIV model identified **FBXO34** as a host factor whose activation promotes latent HIV reactivation. The study then used **affinity purification mass spectrometry** and **co-immunoprecipitation** to identify **hnRNP U** as an FBXO34-interacting protein and presents evidence consistent with FBXO34 promoting **hnRNP U ubiquitination** and **decreasing hnRNP U protein abundance**."
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hnRNP U binds HIV-1 mRNA and suppresses its translation to support latency; FBXO34-driven ubiquitination/degradation of hnRNP U abolishes this interaction and relieves the translational block.
"Mechanistically, the authors report that hnRNP U binds HIV-1 mRNA (Rev element region; amino acids 1–339 of hnRNP U are implicated in the RNA interaction) and **hinders HIV-1 translation**, supporting latency; FBXO34-driven ubiquitination/degradation of hnRNP U abolishes this interaction and thus relieves the translational block."
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In mouse oocytes Fbxo34 regulates meiotic cell-cycle progression upstream of CCNB1/MPF; depletion lowers MPF activity (rescued by CCNB1) while overexpression triggers spindle-assembly-checkpoint activation and metaphase-I arrest, but no direct substrate was identified.
"In mouse oocytes, Fbxo34 perturbation suggests an important role in meiotic cell-cycle progression: depletion causes failure of meiotic resumption associated with low maturation-promoting factor (MPF) activity and can be rescued by exogenous CCNB1; overexpression promotes GVBD but causes SAC activation and MI arrest."
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In mouse oocytes FBXO34 was reported to localize mainly in the nucleus and to colocalize with F-actin during meiotic maturation, providing an orthology-based localization hypothesis for human FBXO34.
"In mouse oocytes, FBXO34 was reported to localize mainly in the **nucleus** and to **colocalize with F-actin** during meiotic maturation."