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Symbol CCNT1 contributors: mct/npt - updated : 03-04-2016
HGNC name cyclin T1
HGNC id 1599
  • a N terminal cyclin domain, N-terminal AAs are specifically involved in the binding of CCNT1 to HEXIM1 but not to HIV1 Tat
  • a coiled-coil motif
  • a His-rich motif
  • a C terminal PEST sequence
  • mono polymer heteromer , dimer
    interspecies homolog to murine Ccnt1
    homolog to C.elegans F44B9.3
  • cyclin family
  • cyclin C subfamily
  • CATEGORY regulatory , transcription factor
    SUBCELLULAR LOCALIZATION     intracellular
    intracellular,nucleus,nucleoplasm,nuclear bodies,nuclear speckles
    text active form of CCNT1 resides in nuclear speckles and raises the possibility that speckles are sites of CCNT1 function and exchange between negative and positive CCNT1 regulatory complexes
    basic FUNCTION
  • HIV1 expression control
  • playing an active role during lymphoid differentiation through germinal center reaction
  • active role for the CDK9/CCNT1 complex during lymphoid differentiation through germinal center reaction
  • required for RNA polymerase II transcription elongation (Diribarne 2009)
  • functions to induce the elongation step of RNA polymerase II transcription by phosphorylating the carboxyl-terminal domain of the largest subunit of RNA polymerase
  • role for this protein in controlling cell cycle probably via RB/E2F1 pathway
  • CELLULAR PROCESS nucleotide, transcription, elongation
    a component
  • CDK9 (catalytic subunit) and CCNT1 (regulatory subunit) make positive transcription elongation factor B (ptefb)
  • part of CCNT1/HEXIM1/RN7SK complexes (RN7SK is released from CCNT1/HEXIM1/RN7SK complexes upon an arrest in transcription and physiological stimulations such as cardiac hypertrophy, leading to CCNT1 activation)(Diribarne 2009)*
  • super elongation complex (SEC) consists of the POLR2A elongation factors ELL, CCNT1 and several frequent KMT2A translocation partners (PMID;
  • CCNT1 is stored in the 7SK ribonucleoprotein (RNP) that contains the three nuclear proteins HEXIM1, LARP7, and MEPCE
    small molecule
  • RNA polymerase II associated
  • interacting with HIV-1Tat and mediating its high affinity to TAR
  • CDK9
  • associates with HEXIM1 to regulate RNA polymerase II elongation of nascent mRNA transcripts (HEXIM1 recognizes the Cyclin T1 subunit, which is a key step toward the regulation of transcription elongation)
  • BRD4 and HEXIM1 proteins interact with CCNT1 at or very near speckle domain
  • mechanism of release of CCNT1 and HEXIM1 from the RN7SK snRNP by viral and cellular activators includes a conformational change in RN7SK
  • transcription of the HIV-1 requires the interaction of CCNT1 subunit of a host cellular factor, with the viral Tat protein at the transactivation response (TAR) element of nascent viral transcripts
  • mediates the transition from transcription initiation to productive elongation by phosphorylation of the C-terminal domain of RNA polymerase II, and is negatively regulated by the cellular protein HEXIM1
  • CDK9 the kinase of CCNT1 stimulates transcription elongation by phosphorylating POLR2A and transcription elongation factors
  • crucial role for the HEXIM1/CCNT1 pathway in the regulation of satellite cell–mediated muscle regeneration
  • LARP7 suppresses CCNT1 activity to inhibit breast cancer progression and metastasis
  • HEXIM1 binds to the CDK9 catalytic site to inhibit CCNT1
  • TAT promotes the release of CCNT1 from the 7SK RNP through direct binding to the 7SK RNA
  • HEXIM1 in addition to its action on CCNT1, plays a role in a variety of different mechanisms: it controls the stability of transcription factor components and assists binding of transcription factors to their targets
  • MEPCE binds chromatin through the histone H4 tail to serve as a CCNT1 activator at specific genes important for cellular identity
  • cell & other