YBX1 is one of the most evolutionarily conserved nucleic acid binding proteins. Initially, it was thought to bind only the conserved Y-box element in double stranded DNA (dsDNA). However, subsequent research has shown its ability to bind to single stranded DNA (ssDNA), damaged DNA, and RNA. In adult human cells, depending on its localization, the functions and protein–protein interactions of YBX1 differ. Nuclear localization of YBX1 promotes the transcription of genes containing the Y box consensus sequence in their promoter region. The target genes of YBX1 exert a broad scope of functions including transcriptional regulation, mRNA packaging, and DNA repair.