Component of the FACT complex, a general chromatin factor that acts to reorganize nucleosomes. The FACT complex is involved in multiple processes that require DNA as a template such as mRNA elongation, DNA replication and DNA repair. During transcription elongation the FACT complex acts as a histone chaperone that both destabilizes and restores nucleosomal structure. It facilitates the passage of RNA polymerase II and transcription by promoting the dissociation of one histone H2A-H2B dimer from the nucleosome, then subsequently promotes the reestablishment of the nucleosome following the passage of RNA polymerase II. Transcription elongation is promoted by the repression of transcription initiation from cryptic sites. Also acts in establishing transcription initiation complexes and promotes SPT15/TBP-binding to a TATA box. Together with replication factor-A protein (RPA), FACT may play a role in nucleosome deposition during DNA replication