Taxonomic distribution of proteins containing SPT16 domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing SPT16 domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

The yeast FACT complex has a role in transcriptional initiation.

Biswas D, Yu Y, Prall M, Formosa T, Stillman DJ
Mol Cell Biol. 2005; 25: 5812-22

A crucial step in eukaryotic transcriptional initiation is recognition of thepromoter TATA by the TATA-binding protein (TBP), which then allows TFIIA andTFIIB to be recruited. However, nucleosomes block the interaction between TBP andDNA. We show that the yeast FACT complex (yFACT) promotes TBP binding to a TATAbox in chromatin both in vivo and in vitro. The SPT16 gene encodes a subunit ofyFACT, and we show that certain spt16 mutations are synthetically lethal with TBPmutants. Some of these genetic defects can be suppressed by TFIIA overexpression,strongly suggesting a role for yFACT in TBP-TFIIA complex formation in vivo.Mutations in the TOA2 subunit of TFIIA that disrupt TBP-TFIIA complex formationin vitro are also synthetically lethal with spt16. In some cases this spt16 toa2 lethality is suppressed by overexpression of TBP or the Nhp6 architecturaltranscription factor that is also a component of yFACT. The Spt3 protein in theSAGA complex has been shown to regulate TBP binding at certain promoters, and we show that some spt16 phenotypes can be suppressed by spt3 mutations. Chromatinimmunoprecipitations show TBP binding to promoters is reduced in single spt16 andspt3 mutants but increases in the spt16 spt3 double mutant, reflecting the mutualsuppression seen in the genetic assays. Finally, in vitro studies show that yFACTpromotes TBP binding to a TATA sequence within a reconstituted nucleosome in aTFIIA-dependent manner. Thus, yFACT functions in establishing transcriptioninitiation complexes in addition to the previously described role in elongation.

The chromatin-specific transcription elongation factor FACT comprises human SPT16and SSRP1 proteins.

Orphanides G, Wu WH, Lane WS, Hampsey M, Reinberg D
Nature. 1999; 400: 284-8

The regulation of gene expression depends critically upon chromatin structure.Transcription of protein-coding genes can be reconstituted on naked DNA with onlythe general transcription factors and RNA polymerase II. This minimal systemcannot transcribe DNA packaged into chromatin, indicating that accessory factors may facilitate access to DNA. Two classes of accessory factor, ATP-dependentchromatin-remodelling enzymes and histone acetyltransferases, facilitatetranscription initiation from chromatin templates. FACT (for facilitateschromatin transcription) is a chromatin-specific elongation factor required fortranscription of chromatin templates in vitro. Here we show that FACT comprises anew human homologue of the Saccharomyces cerevisiae Spt16/Cdc68 protein and thehigh-mobility group-1-like protein structure-specific recognition protein-1.Yeast SPT16/CDC68 is an essential gene that has been implicated in transcription and cell-cycle regulation. Consistent with our biochemical analysis of FACT, weprovide evidence that Spt16/Cdc68 is involved in transcript elongation in vivo.Moreover, FACT specifically interacts with nucleosomes and histone H2A/H2Bdimers, indicating that it may work by promoting nucleosome disassembly upontranscription. In support of this model, we show that FACT activity is abrogated by covalently crosslinking nucleosomal histones.