The function of GFI1 (growth factor independent 1 transcriptional repressor, Ensembl gene identifier ENSG00000162676) is as follows. Transcription repressor essential for hematopoiesis (PubMed:11060035, PubMed:17197705, PubMed:17646546, PubMed:18805794, PubMed:19164764, PubMed:20190815, PubMed:8754800). Functions in a cell- context and development-specific manner (PubMed:11060035, PubMed:17197705, PubMed:17646546, PubMed:18805794, PubMed:19164764, PubMed:20190815, PubMed:8754800). Binds to 5'-TAAATCAC[AT]GCA-3' in the promoter region of a large number of genes (PubMed:11060035, PubMed:17197705, PubMed:17646546, PubMed:18805794, PubMed:19164764, PubMed:20190815, PubMed:8754800). Component of several complexes, including the EHMT2-GFI1-HDAC1, AJUBA-GFI1-HDAC1 and RCOR-GFI-KDM1A- HDAC complexes, that suppress, via histone deacetylase (HDAC) recruitment, a number of genes implicated in multilineage blood cell development (PubMed:16287849). Regulates neutrophil differentiation, promotes proliferation of lymphoid cells, and is required for granulocyte development (PubMed:12778173). Inhibits SPI1 transcriptional activity at macrophage-specific genes, repressing macrophage differentiation of myeloid progenitor cells and promoting granulocyte commitment (By similarity). Mediates, together with U2AF1L4, the alternative splicing of CD45 and controls T-cell receptor signaling (By similarity). Regulates the endotoxin-mediated Toll-like receptor (TLR) inflammatory response by antagonizing RELA (PubMed:20547752). Cooperates with CBFA2T2 to regulate ITGB1-dependent neurite growth (PubMed:19026687). Controls cell-cycle progression by repressing CDKNIA/p21 transcription in response to TGFB1 via recruitment of GFI1 by ZBTB17 to the CDKNIA/p21 and CDKNIB promoters (PubMed:16287849). Required for the maintenance of inner ear hair cells (By similarity). In addition to its role in transcription, acts as a substrate adapter for PRMT1 in the DNA damage response: facilitates the recognition of TP53BP1 and MRE11 substrates by PRMT1, promoting their methylation and the DNA damage response (PubMed:29651020). {ECO:0000250|UniProtKB:P70338, ECO:0000269|PubMed:11060035, ECO:0000269|PubMed:12778173, ECO:0000269|PubMed:16287849, ECO:0000269|PubMed:17197705, ECO:0000269|PubMed:17646546, ECO:0000269|PubMed:18805794, ECO:0000269|PubMed:19026687, ECO:0000269|PubMed:19164764, ECO:0000269|PubMed:20190815, ECO:0000269|PubMed:20547752, ECO:0000269|PubMed:29651020, ECO:0000269|PubMed:8754800}.