Regulation of Globin Gene Expression and Erythroid Differentiation by Sp/KLF Factors.

Sp/Krüppel-like factor (KLF) family of proteins are characterized by the presence of three highly homologous Cys2His2 type zinc-fingers near the C-terminus that bind GC/CACCC boxes, which are one of the most common regulatory elements found in promoters of many cellular and viral genes. Currently, more than 20 members have been identified in the family. This family of factors plays important roles in cell growth, differentiation, development and homeostasis by regulating the expression of their target genes. The GC and GT/CACCC boxes in the globin gene promoters and the beta globin locus control region play an important role in the tissue- and developmental stage- specific expression of globin genes. We have carried out extensive studies to identify the KLF factors that regulate gamma globin expression and erythroid differentiation. Gene expression analysis revealed that most of the Sp/KLF factors are expressed, albeit at variable levels, in human fetal liver and adult blood cells. To determine the role of the Sp/KLF factors in gamma globin expression and erythroid differentiation, functional studies using systematic RNAi to knockdown selected Sp/KLF factors were performed. We used a lentiviral mediated siRNA expression system for specific silencing selected Sp/KLF factors. Effective knockdown of Sp/KLF factors was achieved as judged by a 70–90% decrease in their mRNA levels in the cells. Analyses of globin gene expression showed that the knockdown of some Sp/KLF factors resulted in changes in globin gene expression in K562 cells. We also observed that knockdown of specific Sp/KLF factors resulted in erythroid differentiation of K562 cells. These results suggest that specific Sp/KLF factors may play a role in regulation of globin gene expression and erythroid differentiation.