Histone chaperone that stabilizes pre-existing histone tetramers and regulates replication-independent histone exchange on chromatin (PubMed:26109053). Required for normal chromatin refolding in the coding region of transcribed genes, and for the suppression of spurious transcription (PubMed:26109053). Binds DNA and histones and promotes nucleosome assembly (in vitro) (PubMed:23378026, PubMed:26109053). Facilitates formation of tetrameric histone complexes containing histone H3 and H4 (PubMed:26109053). Modulates RNA polymerase 1-mediated transcription (By similarity). Binds DNA, with a preference for branched DNA species, such as Y-form DNA and Holliday junction DNA (PubMed:23378026). Interacts with histones (PubMed:23378026). Interacts with a heterotetrameric complex formed by histone H3 and H4, especially when the histone tetramer is not bound to DNA (PubMed:26109053). Interacts with histone H3.3 (PubMed:33857403). The acidic C-terminal domain mediates interaction with histone H3/H4 complexes. The histone binding domain can functionally complement the yeast ortholog in regulating histone exchange and suppression of spurious transcription. Belongs to the SPT2 family. Extended N-terminus.