Component of the NC2 complex which represses RNA polymerase II transcription through binding to SPT15/TBP and thereby inhibiting the assembly of the preinitiation complex. The NC2 complex may also mediate transcriptional activation from TATA-driven promoters through association with SPT15/TBP. Component of the NC2 (negative cofactor 2) complex composed of BUR6 and NCB2. The NC2 complex associates with SPT15/TBP. Interacts with SPT15/TBP. Present with 2950 molecules/cell in log phase SD medium.