SARS-CoV-2 N protein potentiates host NPM1-snoRNA translation machinery to enhance viral replication

Dear Editor,COVID-19(Coronavirus Disease 2019)is causing an unprecedented public health crisis.Protein translation is crucial for virus lifecycle.Nucleocapsid(N)protein is among the most abundant SARS-CoV-2 proteins and highly conserved across coronavirus genus.1 However,its function in subverting host translation machinery is still elusive.

Epigenetic regulation of hematopoietic stem cell homeostasis

As one of the best characterized adult stem cells,hematopoietic stem cell(HSC)homeostasis is of great importance to hematopoiesis and immunity due to HSC’s abilities of self-renewal and multi-lineage differentiation into functional blood cells.However,excessive self-renewal of HSCs can lead to severe hematopoietic malignancies like leukemia,whereas deficient selfrenewal of HSCs may result in HSC exhaustion and eventually apoptosis of specialized cells,giving rise to abnormalities such as immunodeficiency or anemia.How HSC homeostasis is maintained has been studied for decades and regulatory factors can be generally categorized into two classes:genetic factors and epigenetic factors.Although genetic factors such as signaling pathways or transcription factors have been well explored,recent studies have emerged the indispensable roles of epigenetic factors.In this review,we have summarized regulatory mechanisms of HSC homeostasis by epigenetic factors,including DNA methylation,histone modification,chromatin remodeling,non-coding RNAs,and RNA modification,which will facilitate applications such as HSC ex vivo expansion and exploration of novel therapeutic approaches for many hematological diseases.

Small noncoding RNAs play superior roles in maintaining hematopoietic stem cell homeostasis

The maintenance of the mammalian blood system depends on hematopoietic stem cells(HSCs),which are a rare class of adult stem cells with self-renewal and multilineage differentiation capacities.The homeostasis of hematopoietic stem cells is finely tuned by a variety of endogenous and exogenous regulatory factors,and disrupted balance will lead to hematological diseases including leukemia and anemia.Recently,emerging studies have illustrated the cellular and molecular mechanisms underlying the regulation of HSC homeostasis.Particularly,the rapid development of second-generation sequencing technologies has uncovered that many small noncoding RNAs(ncRNAs)are highly expressed in HSCs,including snoRNAs,miRNAs,tsRNAs,circular RNAs,etc.In this study,we will summarize the essential roles and regulatory mechanisms of these small ncRNAs in maintaining HSC homeostasis.Overall,this review provides up-to-date information in the regulation of HSC homeostasis by small ncRNAs,which sheds light into the development of therapeutic strategies against hematopoietic malignancies.