Transplantation of hematopoietic stem cells (HSCs) with a naturally occurring CCR5 mutation confers a loss of detectable HIV-1 in the patient, making ablation of the CCR5 gene in HSCs an ideal therapy for an HIV-1 cure. Although CCR5 disruption has been attempted in CD4 T cells and hematopoietic stem/progenitor cells (HSPCs), efficient gene editing with high specificity and long-term therapeutic potential remains a major challenge for clinical translation. Here, we established a CRISPR/Cas9 gene editing system in human CD34 HSPCs and achieved efficient CCR5 ablation evaluated in long-term reconstituted NOD/Prkdc/IL-2Rγ mice. The CCR5 disruption efficiency in our system remained robust in secondary transplanted repopulating hematopoietic cells. More importantly, an HIV-1 resistance effect was observed as indicated by significant reduction of virus titration and enrichment of human CD4 T cells. Hence, we successfully established a CRISPR/Cas9 mediated CCR5 ablating system in long-term HSCs, which confers HIV-1 resistance in vivo. Our study provides evidence for translating CCR5 gene-edited HSC transplantation for an HIV cure to the clinic.

Tyrosine phosphorylation is a common protein posttranslational modification, which plays a critical role in signal transduction and the regulation of many cellular processes. Using a pro-peptide strategy to increase cellular uptake of O-phosphotyrosine (pTyr) and its nonhydrolyzable analog 4-phosphomethyl-L-phenylalanine (Pmp), we identified an orthogonal aminoacyl-tRNA synthetase/tRNA pair that allows the site-specific incorporation of both pTyr and Pmp into recombinant proteins in response to the amber stop codon in Escherichia coli in good yields. The X-ray crystal structure of the synthetase reveals a reconfigured substrate binding site formed by non-conservative mutations and substantial local structural perturbations. We demonstrate the utility of this method by introducing Pmp into a putative phosphorylation site whose corresponding kinase is unknown and determined the affinities of the individual variants for the substrate 3BP2. In summary, this work provides a useful recombinant tool to dissect the biological functions of tyrosine phosphorylation at specific sites in the proteome.

Members of the GATA protein family play important roles in lineage specification and transdifferentiation. Previous reports show that some members of the GATA protein family can also induce pluripotency in somatic cells by substituting for Oct4, a key pluripotency-associated factor. However, the mechanism linking lineage-specifying cues and the activation of pluripotency remains elusive. Here, we report that all GATA family members can substitute for Oct4 to induce pluripotency. We found that all members of the GATA family could inhibit the overrepresented ectodermal-lineage genes, which is consistent with previous reports indicating that a balance of different lineage-specifying forces is important for the restoration of pluripotency. A conserved zinc-finger DNA-binding domain in the C-terminus is critical for the GATA family to induce pluripotency. Using RNA-seq and ChIP-seq, we determined that the pluripotency-related gene Sall4 is a direct target of GATA family members during reprogramming and serves as a bridge linking the lineage-specifying GATA family to the pluripotency circuit. Thus, the GATA family is the first protein family of which all members can function as inducers of the reprogramming process and can substitute for Oct4. Our results suggest that the role of GATA family in reprogramming has been underestimated and that the GATA family may serve as an important mediator of cell fate conversion.