Tdp1 processes chromate-induced single-strand DNA breaks that collapse replication forks

Area of Science:

• Genetics
• Molecular Biology
• Toxicology

Background:

• Hexavalent chromium [Cr(VI)] is a known carcinogen that induces DNA damage.
• The specific DNA damage responses (DDRs) critical for cellular protection against Cr(VI) remain incompletely understood.

Purpose of the Study:

• To elucidate the toxicogenomic profile of Cr(VI) and identify key DDR pathways involved in chromate resistance.
• To compare the Cr(VI) response to that of camptothecin (CPT), a Topoisomerase 1 inhibitor.

Main Methods:

• Genome-wide quantitative functional profiling in Schizosaccharomyces pombe.
• Measurement of DNA damage responses (DDRs).
• Genetic interaction assays.

Main Results:

• Cr(VI) toxicogenomic profile closely resembles that of CPT, indicating Topoisomerase 1 (Top1) involvement.
• ATR/Rad3-dependent checkpoints and Mus81-dependent sister chromatid recombination (SCR) are crucial for Cr(VI) resistance.
• Base excision repair (BER) and interstrand crosslink (ICL) repair are not essential for chromate resistance.

Conclusions:

• Tdp1 tyrosyl-DNA phosphodiesterase and Pnk1 polynucleotide kinase phosphatase (PNKP) repair critical Cr-induced single-strand breaks (SSBs) that lead to replication fork collapse.
• These repair pathways are essential for preventing chromate toxicity and may be relevant to neurodegenerative diseases.