{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Cyclin T1 (encoded by the CCNT1 gene) is a critical regulatory subunit of the positive transcription elongation factor b (P‐TEFb) complex, which—when partnered with the catalytic CDK9—facilitates the transition of RNA polymerase II from promoter‐proximal pausing into productive elongation by phosphorylating its carboxy‐terminal domain. This activity is pivotal for robust transcriptional responses to both developmental cues and stress signals, as Cyclin T1-containing P‐TEFb is rapidly mobilized from its reversible, inactive state when sequestered in the 7SK small nuclear ribonucleoprotein complex. In addition to its central role in regulating cellular gene expression, Cyclin T1 is co‐opted by viral transactivators (for example, HIV Tat) to overcome pausing and drive efficient viral transcription. Furthermore, Cyclin T1 interacts with a variety of transcription factors and cofactors—including Myc and BRD4—to modulate the expression of genes governing cell growth, differentiation, and oncogenesis. Regulation of Cyclin T1 levels (for instance, via microRNA‐mediated repression) further underscores its importance in fine‐tuning transcriptional outputs in both normal physiology and disease. Collectively, these findings position CCNT1 as an essential integrator of signals that control transcription elongation, thereby linking diverse cellular and viral processes through its participation in P‐TEFb–mediated gene regulation."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "10"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "V T Nguyen, T Kiss, A A Michels, et al. 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