Acts as a transcriptional repressor (By similarity). Has mitogenic activity for fibroblasts (By similarity). Heparin-binding protein (By similarity). Monomer, and domain-swapped homodimer (By similarity). Interacts with nuclear proteins NCL and YBX1/YB1 (By similarity). Secreted by exosomes and is located inside the exosome (By similarity). May also be secreted as free protein via an as yet unknown pathway (By similarity). The PWWP domain harbors the heparin-binding sites and is responsible for DNA-binding, while the C-terminal region is essentially unstructured. The N-terminal region does not contain a typical signal sequence but is required for secretion (By similarity). It also determines exosomal location (By similarity). Sumoylated with SUMO1. Sumoylation prevents binding to chromatin. Phosphorylation at Ser-165 is likely to be required for secretion. Belongs to the HDGF family.