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. Binds specifically to double-stranded DNA. Component of the FACT complex (also known as the DUF complex), a stable heterodimer of ssrp1 and supt16h. May also be a component of a ck2-spt16-ssrp1 complex which forms following UV irradiation, composed of ssrp1, supt16h, csnk2a1, csnk2a2 and csnk2b. The FACT complex may also interact with vcp. Colocalizes with RNA polymerase II on chromatin. Recruited to actively transcribed loci. Belongs to the SSRP1 family. Contaminating sequence. Potential poly-A sequence.