Acts as a transcriptional activator or repressor. Inhibits the transcriptional activation of Zic family proteins ZIC1, ZIC2 and ZIC3. Retains nuclear Zic proteins ZIC1, ZIC2 and ZIC3 in the cytoplasm. Modulates the expression from both cellular and viral promoters. Down-regulates Tat-dependent transcription of the human immunodeficiency virus type 1 (HIV-1) LTR by interacting with HIV-1 Tat and Rev and impairing their nuclear import, probably by rendering the NLS domains inaccessible to importin-beta. Also stimulates activation of human T-cell leukemia virus type I (HTLV-I) LTR. Binds to the axin complex, resulting in an increase in the level of free beta-catenin. Affects axin regulation of the WNT and JNK signaling pathways. Interacts with HAND1; leading to sequester HAND1 into the nucleolus and prevent its activity. Interacts with ZIC2 (By similarity). The C-terminus interacts with AXIN1, the histidine-rich region of CCNT1/cyclin-T and weakly with LEF1 (PubMed:12192039). Interacts with CCNT2 (PubMed:17289077). (Microbial infection) Interacts (via C-terminus) with HIV-1 Tat and Rev. Also shows a granular distribution in the cytoplasm. Weak expression in the nucleus. Expressed in lymphoid organs (spleen, thymus, peripheral blood leukocytes) as well as prostate, uterus and small intestine. The C2H2-type 3, 4 and 5 zinc finger domains are necessary for transcription activation (By similarity). The cysteine-rich C-terminus is involved in its granular distribution in the cytoplasm. Major isoform. Minor isoform. Initiates from a GTG codon. Contains a Nucleolar localization signal at positions 45-63. Belongs to the MDFI family.