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:

Reticuloendotheliosis virus long terminal repeat elements are efficient promoters in cells of various species and tissue origin, including human lymphoid cells. Promiscuous transcriptional activity of the reticuloendotheliosis virus (REV) long terminal repeat (LTR) was detected in transient expression assays using LTR-chloramphenicol acetyltransferase-encoding gene chimeras, and cells of diverse species and tissue type; levels of expression from two different REV LTRs correlate with reports of pathogenicity of the respective viruses in vivo. REVs do not encode a transactivator targeted to the viral LTR, and cells infected with Marek 's disease virus, a herpesvirus with an overlapping host range, do not express factors that preferentially enhance expression from REV or avian sarcoma / leukemia virus LTRs. REV LTRs work efficiently in human lymphoid cells, and are viable alternatives to promoters commonly used for expression of cloned genes. They may also prove useful in the identification of new, ubiquitous cellular transcription factors.
{"CellLine": [], "CellType": ["human lymphoid cells"], "DNA": ["LTR", "viral LTR", "REV LTRs", "reticuloendotheliosis virus (REV) long terminal repeat", "avian sarcoma / leukemia virus LTRs", "the reticuloendotheliosis virus (REV) long terminal repeat (LTR)", "Reticuloendotheliosis virus long terminal repeat elements", "LTR - chloramphenicol acetyltransferase - encoding gene chimeras", "REVs", "reticuloendotheliosis virus (REV)", "promoters", "long terminal repeat (LTR)", "REV", "cloned genes"], "Protein": ["chloramphenicol acetyltransferase", "ubiquitous cellular transcription factors"], "RNA": []}