Regulation of transcription elongation by positive transcription elongation factor b (P-TEFb)
plays a central role in determining the state of cell activation, proliferation, and
differentiation. In cells, P-TEFb exists in active and inactive forms. Its release from the
inactive 7SK small nuclear ribonucleoprotein complex is a critical step for P-TEFb to activate
transcription elongation. However, no good method exists to analyze this P-TEFb
equilibrium in living cells. Only inaccurate and labor-intensive cell-free biochemical assays …