TSC loss distorts DNA replication programme and sensitises cells to genotoxic stress

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Tuberous Sclerosis Complex (TSC) is linked to hyperactive mTORC1 signaling and non-malignant neoplasia.
• TSC-/- cells show increased apoptosis upon exposure to genotoxic stress, possibly due to metabolic deficits.
• The precise mechanisms linking metabolic dysregulation to DNA damage response and cell cycle alterations in TSC-/- cells remain unclear.

Purpose of the Study:

• To investigate the DNA damage response and cell cycle alterations in TSC1-/- fibroblasts under low-dose genotoxic stress.
• To elucidate the nature of replicative stress and its consequences in the absence of functional TSC1.

Main Methods:

• Exposure of TSC1-/- fibroblasts to low-dose genotoxins.
• Analysis of DNA replication stress, checkpoint responses, and chromosomal aberrations.
• Assessment of nucleotide incorporation rates and origin firing.

Main Results:

• TSC1-/- fibroblasts exhibit futile checkpoint responses and unusual replicative stress.
• Replicative stress is characterized by elevated nucleotide incorporation despite modest origin over-firing.
• Loss of TSC1 leads to asymmetric fork progression and increased chromosomal aberrations upon DNA damage.

Conclusions:

• Reduced stress tolerance in TSC-/- cells is primarily due to defects in DNA replication control.
• These defects impose negative selection against genomic instability.
• This impaired DNA damage response may contribute to the benign nature of TSC-mutant tumors.