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:

Isolation of a candidate repressor / activator, NF-E1 (YY-1, delta), that binds to the immunoglobulin kappa 3' enhancer and the immunoglobulin heavy-chain mu E1 site. We have determined that the developmental control of immunoglobulin kappa 3' enhancer (kappa E3') activity is the result of the combined influence of positive-and negative-acting elements. We show that a central core in the kappa E3' enhancer is active at the pre-B-cell stage but is repressed by flanking negative-acting elements. The negative-acting sequences repress enhancer activity in a position-and orientation-independent manner at the pre-B-cell stage. We have isolated a human cDNA clone encoding a zinc finger protein (NF-E1) that binds to the negative-acting segment of the kappa E3' enhancer. This protein also binds to the immunoglobulin heavy-chain enhancer mu E1 site. NF-E1 is encoded by the same gene as the YY-1 protein, which binds to the adeno-associated virus P5 promoter. NF-E1 is also the human homologue of the mouse delta protein, which binds to ribosomal protein gene promoters. The predicted amino acid sequence of this protein contains features characteristic of transcriptional activators as well as transcriptional repressors. Cotransfection studies with this cDNA indicate that it can repress basal promoter activity. The apparent dual function of this protein is discussed.
{"CellLine": [], "CellType": [], "DNA": ["negative - acting elements", "positive - and negative - acting elements", "The negative - acting sequences", "flanking negative - acting elements", "kappa E3\u0027", "negative - acting segment", "negative - acting sequences", "kappa E3\u0027 enhancer", "the negative - acting segment", "adeno - associated virus P5 promoter", "cDNA", "basal promoter", "human cDNA clone", "ribosomal protein gene promoters", "immunoglobulin kappa 3\u0027 enhancer", "immunoglobulin heavy - chain enhancer mu E1 site", "mouse delta protein", "immunoglobulin heavy - chain mu E1 site"], "Protein": ["YY - 1 protein", "transcriptional activators", "transcriptional repressors", "NF - E1", "amino acid sequence", "human homologue", "zinc finger protein", "delta", "YY - 1"], "RNA": []}