{
  "id": 10524781,
  "title": "Highly inducible transcription is impaired in cells lacking Cyclin T1 (CycT1) of the positive transcription factor b (P-TEFb).",
  "url": "https://urgent.news/2026/09/28/highly-inducible-transcription-is-impaired-in-cells-lacking-cyclin-t1",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-28T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.09.26.754677v1?rss=1"
  },
  "original_language": "en",
  "account": "Eukaryotic cells rely on the positive transcription elongation factor b (P-TEFb) to transition RNA polymerase II (RNAPII) from a paused state to an actively transcribing mode. This complex is formed by the interaction of CDK9 with one of three cyclins: T1, T2a, or T2b. In this study, researchers created cells lacking the CycT1 subunit (CycT1-KO cells) to investigate CycT1's role in cellular transcription.\n\nDespite no noticeable growth issues with the CycT1-KO cells, researchers observed a decrease in CDK9 levels and no compensatory increase in CycT2. This suggested that the reduced functional P-TEFb complexes were sufficient to maintain normal cell growth. Reporter gene assays revealed that NF-kappaB-dependent transcription induced by PMA was impaired in CycT1-KO cells, while AP1-dependent transactivation remained unaffected. Additionally, transcription stimulated by JQ1, a potent P-TEFb inducer, was reduced in the CycT1-KO cells.\n\nBiochemical analysis showed that P-TEFb complexes containing CycT1 (P-TEFb (CDK9:CycT1)) were efficiently released from 7SKsnRNP by JQ1, whereas P-TEFb (CDK9:CycT2) was unaffected by JQ1. Transcriptome analysis indicated a minor impact on steady-state transcription, but JQ1-dependent gene expression was severely diminished in CycT1-KO cells. Notably, among the top 13 JQ1-dependent genes identified in 33 cancer types, 11 were also significantly upregulated in Pancreatic Adenocarcinoma.\n\nTaken together, these findings suggest that while both P-TEFb (CDK9:CycT1) and P-TEFb (CDK9:CycT2) regulate various genes, CycT1 plays a critical role in controlling highly inducible genes, which are also dysregulated in a specific type of cancer.",
  "summary": "In eukaryotic cells, the positive transcription elongation factor b (P-TEFb) plays a critical role in the transition of RNAPII from the paused state to actively transcribing mode. Although three different cyclin (Cyc) T (CycT1, T2a, and T2b) interact with CDK9 to form functional P-TEFb, a majority of P-TEFb complexes are comprised of the CycT1 and CDK9. To analyze the role of the CycT1 subunit of…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 2,
    "also_reported_by": [
      {
        "outlet": "bioRxiv",
        "title": "Constitutively-active Positive Transcription Factor b (P-TEFb) prevents viral latency.",
        "url": "https://urgent.news/2026/09/28/constitutively-active-positive-transcription-factor-b-p-tefb-prevents",
        "published": "2026-09-28T00:00:00.000Z"
      }
    ]
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}