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. Author manuscript; available in PMC: 2012 Jan 1.
Published in final edited form as: Curr Opin HIV AIDS. 2011 Jan;6(1):4–11. doi: 10.1097/COH.0b013e328340ffbb

Figure 4. Control of P-TEFb by Tat.

Figure 4

In resting CD4+ T-cells the majority of the P-TEFb in cells is found in a transcriptionally inactive snRNP complex containing 7SK RNA, HEXIM and the RNA binding proteins MePCE and LARP7. Tat disrupts this complex by displacing HEXIM and forming a stable complex with P-TEFb. Prior to recruitment to the transcription complex a larger complex is formed between P-TEFb and transcription elongation factors from the mixed lineage leukemia (MLL) family, including ELL2. A small fraction of the Tat in cell is also able to form a complex with 7SK RNA in the absence of HEXIM1.