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:

A novel B cell-derived coactivator potentiates the activation of immunoglobulin promoters by octamer-binding transcription factors. A novel B cell-restricted activity, required for high levels of octamer / Oct-dependent transcription from an immunoglobulin heavy chain (IgH) promoter, was detected in an in vitro system consisting of HeLa cell-derived extracts complemented with fractionated B cell nuclear proteins. The factor responsible for this activity was designated Oct coactivator from B cells (OCA-B). OCA-B stimulates the transcription from an IgH promoter in conjunction with either Oct-1 or Oct-2 but shows no significant effect on the octamer / Oct-dependent transcription of the ubiquitously expressed histone H2B promoter and the transcription of USF-and Sp1-regulated promoters. Taken together, our results suggest that OCA-B is a tissue -, promoter -, and factor-specific coactivator and that OCA-B may be a major determinant for B cell-specific activation of immunoglobulin promoters. In light of the evidence showing physical and functional interactions between Oct factors and OCA-B, we propose a mechanism of action for OCA-B and discuss the implications of OCA-B for the transcriptional regulation of other tissue-specific promoters.
{"CellLine": ["HeLa cell"], "CellType": ["B cells"], "DNA": ["an IgH promoter", "tissue - specific promoters", "USF - and Sp1 - regulated promoters", "octamer", "immunoglobulin heavy chain (IgH) promoter", "ubiquitously expressed histone H2B promoter", "IgH promoter", "immunoglobulin promoters", "Oct"], "Protein": ["novel B cell - derived coactivator", "tissue - , promoter - , and factor - specific coactivator", "OCA - B", "Oct factors", "octamer - binding transcription factors", "histone H2B", "fractionated B cell nuclear proteins", "Oct - 1", "Oct - 2", "Oct coactivator"], "RNA": []}