Simian virus 40 large T antigen disrupts genome integrity and activates a DNA damage response via Bub1 binding

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Simian virus 40 (SV40) large T antigen (LT) is crucial for viral replication and oncogenesis.
• SV40 infection induces DNA damage response (DDR) signaling, essential for viral replication.
• The sufficiency of LT in inducing DDR and its genetic requirements were previously unclear.

Purpose of the Study:

• To determine if SV40 LT alone can induce DNA damage response signaling.
• To investigate the genetic requirements and functional consequences of LT-induced DDR.
• To elucidate the role of LT in genome integrity and cellular processes like p53 stabilization and tetraploidy.

Main Methods:

• Expression of SV40 LT in monkey or human cells without a replication origin.
• Assessment of key DDR markers such as gamma-H2AX and 53BP1 foci.
• Analysis of downstream DDR signaling components (chk1, chk2) and mediator proteins (Claspin).
• Investigation of LT binding interactions with Bub1 and retinoblastoma protein.
• Evaluation of p53 phosphorylation at Ser15 and induction of tetraploidy.

Main Results:

• LT expression alone induced gamma-H2AX, 53BP1 foci, and downstream DDR signaling (chk1, chk2).
• LT bound Claspin and its DDR induction primarily depended on Bub1 binding, not retinoblastoma protein.
• LT-induced DDR promoted p53 stabilization via phosphorylation at Ser15.
• LT induced tetraploidy, also dependent on Bub1 binding.

Conclusions:

• SV40 LT is sufficient to initiate DDR signaling, mediated by Bub1 binding.
• LT breaches genome integrity mechanisms, leading to DDR, p53 stabilization, and tetraploidy.
• LT-induced genome instability contributes to the oncogenic potential of SV40.