SSRP1

SSRP1, Structure-specific recognition protein 1, is a eukaryotic protein that functions as a subunit of the FACT (Facilitates Chromatin Transcription) complex, a histone chaperone that modulates nucleosome structure during transcription, replication, and repair. The FACT complex consists of SSRP1 and SPT16 and works to reorganize nucleosomes so RNA polymerase II can pass through chromatin and then reassemble the nucleosome after transcription.

SSRP1 contains regions that support DNA binding and histone interactions. In cooperation with SPT16, SSRP1 helps destabilize the nucleosome, enabling transcription elongation, while also participating in chromatin reassembly following passage of the transcription machinery. Beyond transcription, FACT/SSRP1 is implicated in DNA replication and the DNA damage response, reflecting its broad role in maintaining chromatin dynamics in actively dividing cells.

Gene and expression: In humans, SSRP1 is encoded by the SSRP1 gene. Expression is widespread but tends to be higher in proliferating tissues and in certain cancers, where FACT activity supports transcriptional programs associated with growth.

Clinical relevance: Elevated SSRP1 expression has been observed in several cancers and is sometimes linked to disease progression. Because FACT facilitates transcription of many genes necessary for tumor growth, inhibitors targeting FACT, including curaxins such as CBL0137, have been explored as potential anticancer agents.

Evolution and research: SSRP1 is conserved among eukaryotes and is considered essential for viability in some model systems, underscoring its core role in managing chromatin during transcription and replication.