Transcriptional repressor (PubMed:10488076). Acts on the C- type natriuretic peptide (CNP) promoter (PubMed:9022669). Acts to promote CASP3-mediated apoptosis (PubMed:18325344). Positively regulates TGF-beta signaling by interacting with SMAD7 which inhibits binding of SMAD7 to TGFBR1, preventing recruitment of SMURF ubiquitin ligases to TGFBR1 and inhibiting SMURF-mediated ubiquitination and degradation of TGFBR1 (PubMed:21791611). Contributes to enhancement of TGF-beta signaling by binding to and modulating the transcription activator activity of SMAD4 (PubMed:15881652). Promotes TGF-beta- induced transcription of COL1A2; via its interaction with TFE3 at E- boxes in the gene proximal promoter (By similarity). Plays a role in the repression of hematopoietic precursor cell growth (By similarity). Promotes IL2 deprivation-induced apoptosis in T-lymphocytes, via repression of TSC22D3/GILZ transcription and activation of the caspase cascade (PubMed:26752201). {ECO:0000250|UniProtKB:P62500, ECO:0000269|PubMed:10488076, ECO:0000269|PubMed:15881652, ECO:0000269|PubMed:18325344, ECO:0000269|PubMed:21791611, ECO:0000269|PubMed:26752201, ECO:0000269|PubMed:9022669}. [Isoform 1]: May act to negatively regulate TGFB3 signaling and thereby inhibit cell death in mammary gland cells. . [Isoform 2]: Positively regulates cell death in response to TGFB3 during mammary gland involution. . This is the function of TSC22D1 (TSC22 domain family member 1, ENSG00000102804).