My research is focused on the molecular biology of late myeloid differentiation. Investigations in my lab are in the general areas of myeloid specific gene transcription and regulation of myeloid differentiation by specific transcription factors. One of the areas of investigation in my lab is transcriptional regulation of the genes encoding respiratory burst oxidase component proteins. The two genes that we have been studying are the CYBB and NCF2 genes, which encode the gp91PHOX and p67PHOX proteins, respectively. These genes are transcriptionally active only in phagocytic after the promyelocyte stage of differentiation. Transcription of these genes continues until cell death, and is increased by inflammatory mediators such as IFN-gamma, TNF-alpha and LPS. Therefore, transcription of these genes is lineage, differentiation stage and activation state specific. Since transcription of these two genes occurs at the same time, we have been investigating the hypothesis that homologous cis elements in the two genes are regulated by common transcription factors. Some of the investigations in the lab involve further characterization of cis elements and cognate DNA binding proteins in the CYBB and NCF2 genes.
Our investigations indicate that CYBB and NCF2 transcription requires interaction of the transcription factors PU.1, IRF1 and ICSBP with homologous cis elements in the proximal promoters of both genes. We plan to investigate the role of ICSBP tyrosine phosphorylation in regulation of late myeloid differentiation, in part by using myeloid cells from ICSBP -/- mice (generated by other investigators). We also determined that the transcription factor HoxA10 represses the CYBB and NCF2 genes in undifferentiated myeloid cells. Current investigations focus on characterization of this repression, in terms of recruitment of histone deacetylases. In other studies, we determined that the protein tyrosine phosphatase SHP1 antagonizes CYBB and NCF2 transcription in myeloid cells. Further investigations of whether IRF1, ICSBP and HoxA10 are SHP1-PTP substrates are underway.
Publications:
Eklund, E.A., Kakar, R.: Identification and characterization of TF1-phox, a DNA binding protein that increases expression of gp91-phox in PLB985 myeloid leukemia cells (1997) J. Biol. Chem 272, 9344-9355.
Eklund, E. A., Jalava, A., Kakar, R.: PU.1, interferon regulatory factor 1, and interferon consensus sequence binding protein cooperate to increase gp91phox expression. (1998) J. Biol. Chem. 273, 13957-13965.
Eklund, E. A., Kakar, R.: Recruitment of CBP by PU.1, IRF1 and ICSBP is necessary for gp91phox and p67phox expression (1999) J. Immunol. 163, 6095-6105.
Eklund, E. A., Jalava, A., Kakar, R.: Tyrosine phosphorylation of HoxA10 decreases DNA-binding and transcriptional repression during IFNg induced differentiation of myeloid leukemia cell lines. (2000) J. Biol. Chem. 275, 20117-20126.
Kautz, B, Jalava, A, Eklund, EA: SHP1 protein tyrosine phosphatase inhibits transcription of the CYBB and NCF2 genes in undifferentiated myeloid cell lines by inhibiting interaction of PU.1, IRF1, ICSBP and CBP. (2001) J. Biol. Chem., In press.
