Spt16

Spt16 is a eukaryotic protein component of the FACT complex, which stands for Facilitates Chromatin Transcription. In most eukaryotes, Spt16 forms a heterodimer with Pob3 in yeast or with SSRP1 in mammals to compose FACT. The complex functions as a histone chaperone that reorganizes nucleosomes to enable RNA polymerase II to transcribe through chromatin. FACT promotes disassembly of H2A-H2B dimers and reassembly behind the polymerase, thereby preserving chromatin integrity and regulating transcription elongation. It also participates in DNA replication and repair by modulating nucleosome dynamics at stalled forks and damage sites.

The Spt16 protein is primarily nuclear and conserves interaction surfaces for histones and for Pob3/SSRP1. In Saccharomyces cerevisiae, the gene is SPT16; in humans, the homolog is SUPT16H. The other subunit is Pob3 in yeast; SSRP1 in vertebrates. The FACT complex is essential for viability in several organisms; depletion impairs transcription, chromatin structure, and genome stability. Spt16 contains conserved domains implicated in histone binding and chromatin interaction, contributing to the complex’s ability to destabilize and reassemble nucleosomes during transcription, replication, and repair.