Wdr5Controls The Expression Of γ-globin And Its Own Gene Regulation

Thalassemia and Sickle cell diseases are two kinds of worldwide spreading hereditary diseases. Mutations in hemoglobin result in the decrease of the oxygen-carrying capacity, which seriously endangers the health or even lives. Today, the treatments for anemia include blood transfusion, splenectomy, bone marrow transplantation etc., but not satisfactory. Upregulating the expression of y-globin to replace mutated β-globin could greatly alleviate the symptoms of anemia, becoming a better choice for treatment. In this study, we focused on investigating how WDR5regulated the expression of y-globin and its own regulatory mechanisms, providing the mechanismistic basis for anemia treatment.WDR5is an essential component of the MLL (mixed lineage leukemia) complex, which triggers histone methylation at lysine4of histone3preferentially as an active epigenetic mark at5’coding region of the gene. In Chapter Two, we show that WDR5interacts with NF-E4in a PRMT5-dependent manner and is essential for H3K4me3at the y-globin promoters in K562cells. Enforced expression of WDR5in K562cells reduces y-globin gene expression, whereas knockdown of WDR5increases y-globin gene expression. Consistent with this, both histone H3and H4acetylation at the y-globin promoters are increased while histone H3K9methylation is decreased in WDR5knockdown cells compared to the control. Hemin treatment, mutant WDR5and DNA methylation assay strongly supported the results. We demonstrate that WDR5is able to interact with HDAC1and a PHD domain-containing protein, ING2(inhibitor of growth), an H3K4me3mark "reader" enhancing y-globin gene transcriptional repression. In human adult bone marrow erythroid progenitor cells, the highly enriched levels of WDR5on the y-promoters compared to those from cord blood and other globin gene loci in bone marrow indicate its developmental importance. Taken together, our findings provide a novel mechanism by which H3K4me3induced by WDR5at the y-globin promoters may be primed to recruiting the ING2-associated HDAC1component, thereby silencing the y-globin gene expression.In Chapter Three, we went on studying WDR5’s own gene expression modulation. We first use the promoter prediction softwares (TFscan and Consite) to scan WDR5promotor and found there are two SRY binding sites. SRY activates WDR5promoter through binding to these sites, whose mutations lead to reduced binding by SRY. ChIP and EMSA experiments demonstrate that SRY binds the WDR5promoter directly. WDR5transcripts as well as WDR5protein levels are up-regulated when SRY is overexpressed in LNCaP cells. Consistent with this, both H3K4me2and H3K4me3marks at the y-globin promoters are increased compared to the control. We found that WDR5is associated with SRY on its own promoter, and further confirmed that WDR5increases its own expression by feedback mechanism. In addition, SRY cooperates with WDR5to induce the expression of SOX9, which may be important for sex determination. Taken together, our findings show that SRY activates WDR5, and they activate the expression of SOX9synergetically.In conclusion, the current study demonstrates that:(1) WDR5plays an important role in silencing y-globin expression.(2) WDR5is modulated by SRY, and they synergetically activates the expression of SOX9, which could be important for sex determination...