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Specific replication factors are targeted by different genotoxic agents to inhibit replication
Aparna Sharma1, Ananya Kar, Manpreet Kaur
1National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
Abstract:
When mammalian cells experience DNA damaging stress, they block DNA replication to avoid erroneous replication of the damaged template. The cells that are unable to respond to DNA damage continue faulty DNA replication that results in incorporation of genomic lesions. To understand the regulation of replication machinery during stress, systemic studies have been carried out but they have been restricted to the evaluation of the mRNA levels and therefore have not been able to identify post-transcriptional changes, vital for immediate blocking of the progressing DNA replication. We have recently discovered that an essential replication factor is downregulated by radiation stress. In this study, we have carried out a systematic evaluation of protein levels of entire replication apparatus after different types of DNA damage. We report that, independent of the status of p53 and retinoblastoma protein, mammalian cells choose targets that are essential for prereplication, preinitiation, and elongation phases of replication. We imposed different kinds of stress to discern whether similar or unique responses are invoked, and we propose a model for inhibition of replication machinery in which mammalian cells target specific essential replication factors based on the experienced stress.
Insights
Mammalian cells halt DNA replication during stress by downregulating key replication proteins, regardless of p53 or retinoblastoma protein status. This post-transcriptional control prevents further DNA damage.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- DNA replication must be tightly regulated during cellular stress to prevent genomic instability.
- Previous studies focused on mRNA levels, missing crucial post-transcriptional regulation of replication.
- Mammalian cells employ mechanisms to block DNA replication under genotoxic stress.
Purpose of the Study:
- To systematically investigate protein-level changes in the replication machinery following DNA damage.
- To identify specific replication factors targeted during stress response.
- To elucidate the role of post-transcriptional regulation in blocking DNA replication.
Main Methods:
- Quantitative proteomics to analyze protein levels of the replication apparatus.
- Application of various DNA-damaging agents (e.g., radiation).
- Assessment of protein downregulation independent of p53 and retinoblastoma protein (Rb) status.
Main Results:
- Mammalian cells downregulate essential replication factors involved in prereplication, preinitiation, and elongation.
- This downregulation occurs irrespective of p53 and Rb protein status.
- Different types of DNA damage trigger specific, yet overlapping, targeting of replication factors.
Conclusions:
- Mammalian cells utilize post-transcriptional mechanisms to inhibit DNA replication machinery during stress.
- Specific replication factors are selectively targeted based on the type of DNA damage.
- A model is proposed for stress-induced inhibition of replication involving targeted downregulation of essential factors.
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