Practice question

FACT, facilitates chromatin transcription, is heterodimeric histone chaperone composed of SPT16 and SSRP1 in humans, Spt16-Pob3 plus Nhp6 in yeast, that remains associated with elongating Pol II during gene body transcription. Nucleosomes present strong barrier to polymerase progression, causing frequent pausing and backtracking requiring rescue. FACT binds both H2A-H2B dimers and H3-H4 tetramers simultaneously via acidic domains, destabilizing nucleosome without displacing octamer completely, allowing passage. Interaction with SPT5 DSIF complex and PAF1 complex tethers FACT to elongating polymerase ensuring rapid reassembly behind transcription machinery.