Distal regulation of c-myb expression in human myeloid leukemia cells

The transcription factor c-Myb a key regulator in proliferation and differentiation of hematopoietic progenitor cells, is precisely regulated during essential cellular processes. Overexpression and rearrangement of c-myb has been reported in human tumors including myeloid leukemia, but exact regulatory mechanisms have remained elusive. Here, we identified, using 4C assay with the c-myb promoter as an anchor, the interaction site at -34k region upstream of c-myb gene that are involved in c-myb expression. Furthermore, we found that the long-range interactions changed with c-myb being down-regulated on differentiation progress in human myeloid leukemia cell lines. Taken together, our date revealed that a potential c-myb enhancer-promoter interactions may be a particularly important regulatory mechanism for c-myb gene expression in human myeloid leukemia cells. Overall design: We used human myeloid leukemia cell lines K562, U937 and HL60 to carry out 4C-seq experiments, as a control, we carried out parallel 4C measurements in HeLa cells, the c-myb promoter fragment served as a bait fragment to detect the long-range interactions. To validate the presence of potential enhancers in Hbs1l-Myb intergenic region that regulate c-myb transcription by physically interacting with the c-myb promoter via chromatin looping, 4C-Seq was subsequently carried out using the c-myb promoter as viewpoint in K562, U937 and HL60 cells before and after differentiation, representing stages of high and low c-myb expression, respectively.