title: Analysis of the DNA-binding and transcriptional activation functions of human Fli-1 protein.
abstract: Three of the ets oncogene superfamily members v-ets, Spi-1/PU.1 and Fli-1, have been shown to be directly involved in retroviral-mediated acute erythroleukemias. The Fli-1 gene was found to be rearranged in 75% of the erythroleukemias induced by Friend murine leukemia virus (F-MuLV), suggesting that it could play a key role in cellular transformation. We have previously isolated and characterized the human Fli-1 gene and have found it to be highly homologous (80%) to the human erg-2 gene. Human Fli-1 was also shown to be rearranged in Ewing's sarcoma cases, in which the amino-terminal region of the Fli-1 gene was replaced with a novel coding region of a putative RNA-binding protein, EWS. In this report, we show that the recombinant Fli-1 protein expressed in bacteria binds to DNA in a sequence-specific manner. It appears that Fli-1 and erg proteins fall into the category of ets proteins that recognize limited ets target sequences, unlike c-ets-1, ets-2 and Elk-1. The Fli-1 gene was found to activate the transcription of the reporter gene that was linked to Fli-1 target sequences, suggesting that Fli-1 is a sequence-specific transcriptional activator. Deletion analysis revealed the presence of two autonomous transcriptional activation domains, one at the amino-terminal region (amino-terminal transcriptional activation domain, ATA) and the other at the carboxy-terminal region (carboxy-terminal transcriptional activation domain, CTA). Secondary structural analysis of ATA and CTA domains revealed the presence of helix-loop-helix (H-L-H) and/or turn-loop-turn (T-L-T) regions. From these results it appears that a portion of the Fli-1 ATA domain (H-L-H region) was replaced by the amino-terminal domain of EWS gene in Ewing's sarcoma cases. Therefore alteration in the transcriptional activation function of Fli-1 may be responsible for human malignancies such as sarcomas, leukemias and lymphomas in which this gene is rearranged.
authors.affiliation: Jefferson Cancer Institute, Philadelphia, Pennsylvania 19107.
authors.forename: V N
authors.initials: VN
authors.lastname: Rao
authors.forename: T
authors.initials: T
authors.lastname: Ohno
authors.forename: D D
authors.initials: DD
authors.lastname: Prasad
authors.forename: G
authors.initials: G
authors.lastname: Bhattacharya
authors.forename: E S
authors.initials: ES
authors.lastname: Reddy
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015321:Gene Rearrangement; D006801:Humans; D008969:Molecular Sequence Data; D009857:Oncogenes; D017433:Protein Structure, Secondary; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D012512:Sarcoma, Ewing / Q000235:genetics; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D004268:DNA-Binding Proteins; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D004247:DNA