New Study Reveals Critical DNA Repair Mechanism That Prevents UV-Induced Skin Cancer

Breakthrough in Understanding DNA Repair Mechanisms

Researchers have identified a critical mechanism through which cells repair UVB-induced DNA damage, according to a recent study published in Nature Communications. The investigation reveals how the protein And-1 coordinates with polymerase δ to regulate nucleotide excision repair (NER), the primary pathway for removing UV-induced DNA lesions. This discovery provides significant insights into the molecular processes that prevent UVB-induced skin tumorigenesis, sources indicate.

Breakthrough in Understanding DNA Repair Mechanisms
And-1’s Direct Role in UV Damage Repair
Coordination with Key NER Factors
Mechanism of Polymerase δ Recruitment
Phosphorylation-Dependent Regulation
Structural Insights and Conformational Changes
Implications for Skin Cancer Prevention

And-1’s Direct Role in UV Damage Repair

The study demonstrates that And-1 physically accumulates at sites of UV-induced DNA damage, according to the research findings. Through immunofluorescence analysis in multiple cell types including primary human epidermal keratinocytes, immortalized human keratinocyte cells, and primary human fibroblast cells, scientists observed And-1 co-localizing with both cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) – the two major types of DNA damage caused by UVB exposure.

Experimental results showed that And-1 depletion significantly compromised cells’ ability to remove both CPDs and 6-4PPs, the report states. Cells lacking adequate And-1 expression demonstrated increased sensitivity to UVB treatment, while ectopic expression of And-1 effectively restored cell viability, ruling out potential off-target effects.

Coordination with Key NER Factors

Mass spectrometry analysis identified several NER factors interacting with And-1, including DDB1 and POLD1/p125, according to the research. Co-immunoprecipitation assays confirmed that both endogenous and exogenous And-1 interacted with these critical repair proteins, with interactions significantly enhanced following UVB exposure.

The timing of protein recruitment to chromatin provided crucial insights, analysts suggest. While DDB1 rapidly accumulated at chromatin within approximately 5 minutes and diminished within an hour after UVB exposure, And-1 and p125 began accumulating at 5-10 minutes, reaching maximum levels at 4 and 8 hours respectively. This temporal pattern indicates that And-1 functions during the later stages of NER, particularly during gap-filling DNA synthesis.

Mechanism of Polymerase δ Recruitment

The research reveals that And-1 specifically facilitates the recruitment of p125 (the catalytic subunit of polymerase δ) to UV lesion sites by enhancing its interaction with proliferating cell nuclear antigen (PCNA), according to the findings. And-1 depletion significantly impaired chromatin accumulation of p125 but not DDB1, while ectopic expression restored p125 association.

Further investigation showed that And-1 also interacts with p66, another essential component for recruiting p125 to UV lesion sites. Depletion of And-1 reduced co-localization of p66 with CPDs and impaired its chromatin association, the report states.

Phosphorylation-Dependent Regulation

The study identifies that phosphorylation of And-1 at T826 by ATR is critical for its function in NER, according to researchers. Phosphorylated And-1 levels significantly increased following UVB exposure, and this modification was essential for its accumulation at UV lesion sites. Reconstitution experiments demonstrated that wild-type And-1, but not the T826A mutant, restored p125 co-localization with CPDs and enhanced CPD removal efficiency.

Notably, the phospho-mimetic T826E mutant partially restored CPD removal even in the presence of ATR inhibition, indicating that phosphorylation of And-1 at T826 represents a primary target of ATR during NER, analysts suggest.

Structural Insights and Conformational Changes

Domain mapping revealed that the SepB domain (330-984) mediates And-1’s interaction with p125, while the HMG domain (984-1129) is responsible for chromatin association, according to the research. Phosphorylation at T826 disrupts intramolecular interactions between these domains, allowing And-1 to bind UV lesion DNA through its HMG domain while interacting with p125 via its SepB domain.

In vitro DNA binding assays showed that purified recombinant And-1 exhibits stronger affinity for single-stranded DNA, DNA bubble structures, and gap DNA than double-stranded DNA. Furthermore, And-1 enhanced p125’s association with gap DNA molecules, the report states.

Implications for Skin Cancer Prevention

This comprehensive investigation provides crucial insights into the molecular mechanisms protecting against UV-induced skin damage, according to analysts. The identification of And-1’s role in coordinating polymerase δ recruitment for gap-filling synthesis during NER offers potential targets for developing strategies to enhance DNA repair capacity and prevent UVB-induced skin tumorigenesis.

The research demonstrates that efficient NER requires precise coordination between damage recognition, excision, and synthesis components, with And-1 serving as a critical bridge between early and late repair stages. Understanding these mechanisms may eventually lead to improved approaches for reducing skin cancer risk, particularly in individuals with compromised DNA repair capacity.