You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["RNA", "CellLine", "Protein", "DNA", "CellType"].

Please return the output as a JSON object of the format: {"DNA" : ["TAL1", ...], "RNA": ["mRNAs", ...], "CellLine": ["T cells", ...], "CellType": ["monocytes", ...], "Protein": ["IL-2", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Cloning and functional characterization of early B-cell factor, a regulator of lymphocyte-specific gene expression. Early B-cell factor (EBF) was identified previously as a tissue-specific and differentiation stage-specific DNA-binding protein that participates in the regulation of the pre-B and B lymphocyte-specific mb-1 gene. Partial amino acid sequences obtained from purified EBF were used to isolate cDNA clones, which by multiple criteria encode EBF. The recombinant polypeptide formed sequence-specific complexes with the EBF-binding site in the mb-1 promoter. The cDNA hybridized to multiple transcripts in pre-B and B-cell lines, but transcripts were not detected at significant levels in plasmacytoma, T-cell, and nonlymphoid cell lines. Expression of recombinant EBF in transfected nonlymphoid cells strongly activated transcription from reporter plasmids containing functional EBF-binding sites. Analysis of DNA binding by deletion mutants of EBF identified an amino-terminal cysteine-rich DNA-binding domain lacking obvious sequence similarity to known transcription factors. DNA-binding assays with cotranslated wild-type and truncated forms of EBF indicated that the protein interacts with its site as a homodimer. Deletions delineated a carboxy-terminal dimerization region containing two repeats of 15 amino acids that show similarity with the dimerization domains of basic-helix-loop-helix proteins. Together, these data suggest that EBF represents a novel regulator of B lymphocyte-specific gene expression.
{"CellLine": ["transfected nonlymphoid cells", "plasmacytoma", "nonlymphoid cell lines", "pre - B", "pre - B and B - cell lines", "T - cell", "B - cell lines"], "CellType": [], "DNA": ["EBF - binding sites", "EBF - binding site", "pre - B and B lymphocyte - specific mb - 1 gene", "cDNA", "mb - 1 promoter", "cDNA clones"], "Protein": ["early B - cell factor", "DNA - binding protein", "basic - helix - loop - helix proteins", "Early B - cell factor (EBF)", "recombinant polypeptide", "Early B - cell factor", "EBF", "EBF -", "dimerization domains", "carboxy - terminal dimerization region", "amino - terminal cysteine - rich DNA - binding domain", "homodimer", "transcription factors"], "RNA": []}