RESUMEN
Transcription factors are a class of proteins that regulate gene transcription and expression by binding to gene-specific sequences and play an essential role in regulating the biological activities of cells. The RHR (Rel-homology region) transcription factor family is the primary member of the IF (immunoglobulin fold) transcription factor superfamily, whose members contain the conserved Rel domain and IPT (immunoglobulin-like fold) domain. As an ancient transcription factor family, the RHR family continues differentiation on gene gain and loss through gene duplication, mutation, and silencing, accompanied with the evolution of diverse species. Natural selection has led to different rates of evolution among members of the family, and some domains of the protein family have shown unique mechanisms of evolution. However, the current reviews about the origin and differentiation of RHR family are rare. In this review, we summarize the research results on the distribution, classification, function, and evolution of the members of the RHR family in order to provide a reference and new idea for studying the evolution mechanism of the whole transcription factor family and the evolutionary relationship among species.