May be involved in transcriptional regulation. Modulates various viral and cellular promoters in a promoter context-dependent manner. For example, transcription from the FOS promoter is increased, while Rous sarcoma virus (RSV) long terminal repeat (LTR) promoter activity is repressed. Does not bind DNA directly. Expressed in all tissues examined. Highly expressed in heart, ovary, prostate and skeletal muscle. Moderately expressed in brain, placenta, testis and small intestine. Weakly expressed in lung, liver and spleen. Expressed in several cancer cell lines. Phosphorylation of Ser-38 and Ser-39 is critical for transcriptional repression. Belongs to the TFS-II family. TFA subfamily.