The K562 cell is being studied as a model of human globin expression. K562 cells express embryonic and fetal hemoglobins, but not hemoglobin A, Beta-globin chains, nor Beta-globin mRNA. Understanding the pattern of globin expression in K562 cells may yield insight into globin expression and hemoglobin switching in normal cells. Previous work in this project has shown that chromosomal alterations do not account for the pattern of Beta-like globin expression seen in the K562 cells. This extends work of other indicating that the Beta-globin gene is normal in the K562 cells. It is not expressed because of the regulatory environment in these cells. This suggests that the observed expression pattern is due to normal regulatory mechanisms and not to a pathological event. This has allowed us to begin investigating the relationship that exists between the chromatin structure and transcriptional ability of the individual Beta-like globin genes (Epsilon, Gamma, Delta, and Beta). The goal of this study is to develop a functional assay for protein factors responsible for tissue specific and developmentally regulated expression of the Beta-globin genes in K562 and other erythroid cells. It has been shown that """"""""soluble chromatin"""""""" can be recovered from induced and uninduced K562 cell nuclei in reasonable yield. These chromatin fragments have been well characterized. They contain the full complement of histone proteins and have normal nucleosomal spacing. In addition, these fragments maintain the transcriptional fidelity found in intact nuclei, i.e., they allow the transcription of Gamma-globin but not Beta-globin genes. These results can now be exploited to produce a functional assay for regulatory factors responsible for the differential globin expression seen in these cells.
