TIF1β is a member of the TIF1 (transcriptional intermediary factor 1) family, a group of transcriptional regulators that play key roles in development and differentiation. Members of this family are characterized by the presence of two conserved motifs – an N-terminal RING-B box-coiled-coil motif and a C-terminal PHD finger and bromodomain unit. TIF1β is a corepressor for KRAB (Kruppel associated box) domain containing zinc finger proteins. The KRAB domain containing zinc finger proteins are a large group of transcription factors that are vertebrate-specific, varied in their expression patterns between species, and thought to regulate gene transcription programs that control speciation. TIF1β has been shown to be essential for early embryonic development and spermatogenesis. It functions to either activate or repress transcription in response to environmental or developmental signals by chromatin remodeling and histone modification. The recruitment and association of TIF1β with heterochromatin protein (HP1) is essential for transcriptional repression, and for progression through differentiation of F9 embryonic carcinoma cells. TIF1β also plays a role in the DNA damage response. Phosphorylation of TIF1β on Ser842 occurs in an ATM-dependent manner in response to genotoxic stress and is thought to be essential for chromatin relaxation, which is in turn required for the DNA damage response.