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. Forms a stable heterodimer with SPT16. The SPT16-POB3 dimer weakly associates with multiple molecules of NHP6 (NHP6A or NHP6B) to form the FACT (yFACT or SNP) complex. The FACT complex interacts with the CK2 (casein kinase II) complex subunits CKA1, CKA2, CKB1 and CKB2 and the components of the transcription machinery CHD1, CTR9, PAF1 and CDC73. The FACT complex interacts with the PAF1 complex. SPT16 interacts with SAS3 and POL1. Interacts directly with RFA1. Colocalizes with RNA polymerase II on chromatin (PubMed:10413469, PubMed:14585989, PubMed:14739930). Recruited to actively transcribed loci (PubMed:14585989). Associates with the coding region of HTA1 (PubMed:19683497). In contrast to the orthologous protein in animals and plants, this protein does not contain a HMG box DNA-binding domain. This function may instead be provided by the HMG box of the associated NHP6A/NHP6B proteins in the FACT complex of yeast. Present with 22400 molecules/cell in log phase SD medium. Belongs to the SSRP1 family.