Large T antigen - P03070 (LT_SV40)


Protein Feature View of PDB entries mapped to a UniProtKB sequence  

  • Number of PDB entries for P03070: 20
Isoform large T antigen is a key early protein essential for both driving viral replication and inducing cellular transformation. Plays a role in viral genome replication by driving entry of quiescent cells into the cell cycle and by autoregulating the synthesis of viral early mRNA. Displays highly oncogenic activities by corrupting the host cellular checkpoint mechanisms that guard cell division and the transcription, replication, and repair of DNA. Participates in the modulation of cellular gene expression preceeding viral DNA replication. This step involves binding to host key cell cycle regulators retinoblastoma protein RB1/pRb and TP53. Induces the disassembly of host E2F1 transcription factors from RB1, thus promoting transcriptional activation of E2F1-regulated S-phase genes. Inhibits host TP53 binding to DNA, abrogating the ability of TP53 to stimulate gene expression. Plays the role of a TFIID-associated factor (TAF) in transcription initiation for all three RNA polymerases, by stabilizing the TBP-TFIIA complex on promoters. Initiates viral DNA replication and unwinding via interactions with the viral origin of replication. Binds two adjacent sites in the SV40 origin. The replication fork movement is facilitated by Large T antigen helicase activity. Activates the transcription of viral late mRNA, through host TBP and TFIIA stabilization. Interferes with histone deacetylation mediated by HDAC1, leading to activation of transcription. May inactivate the growth-suppressing properties of the E3 ubiquitin ligase CUL7. UniProt
Pathway Maps
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Subunit Structure
Isoform large T antigen forms homohexamers in the presence of ATP. Interacts with host HDAC1. Interacts (via LXCXE domain) with host RB1; the interaction induces the aberrant dissociation of RB1-E2F1 complex thereby disrupting RB1's activity. Interacts (via LXCXE domain) with host pRB-related proteins RBL1 and RBL2. Interacts (via C-terminus) with host TOP1 and POLA1 allowing DNA replication. Interacts with host TP53, inhibiting TP53 binding to DNA. Interacts with host preinitiation complex components TBP, TFIIA and TFIID to regulate transcription initiation. LT interacts (via CPD region) with host FBW7gamma isoform (via WD repeats); seems to function as a competitive inhibitor of FBW7gamma function for physiologic substrates. LT interacts with host E3 ubiquitin ligase CUL7; this interaction seems to inhibit CUL7. Component of a SCF(CUL7)-like complex composed of SV40 Lt and host proteins CUL7, SKP1, RBX1, and FBXW8. LT interacts with host BUB1; this interaction induces activation of a DNA damage response and promotes p53 stabilization and phosphorylation (Probable). Interacts with host FAM111A and this interaction is required for efficient viral replication and sustained viral gene expression in restrictive cell types. UniProt
Cdc4 phospho-degron (CPD) region is involved in interaction with host FBW7gamma isoform. UniProt
  • Isoforms: 4 , currently showing only the 'canonical' sequence.
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